Several trucks from a Russian convoy that passed into Ukraine without permission from Kyiv have returned back across the border into Russia.
Witnesses said Saturday other trucks from the more than 220 vehicles that entered Ukraine Friday are arriving at the border, preparing to re-enter Russia. It is not clear if the trucks are carrying any cargo.
On Friday, White House officials said Russia's unauthorized movement of the humanitarian truck convoy into Ukraine is a flagrant violation of Ukraine's sovereignty.
U.S. Deputy National Security Advisor Ben Rhodes said Russia must remove the convoy from eastern Ukraine or face consequences. He said the United States plans to discuss the situation at the U.N. Security Council.
U.N. Secretary-General Ban Ki-moon also voiced concern about the convoy's movement, saying any unilateral action has the potential of exacerbating an already dangerous situation in eastern Ukraine.
U.S Defense Department spokesman John Kirby told reporters the U.S. is very concerned about the trucks crossing the Ukrainian border.
”We strongly condemn this action and any actions that Russian forces take that increase tensions in the region," he said. "Russia should not send vehicles, persons or cargo of any kind into Ukraine, whether under the guise of humanitarian convoys or any other pretext, without Kyiv’s express permission.”
Kirby stopped short of calling the move an invasion, but said it amounts to a violation of Ukraine’s sovereignty and territorial integrity.
“Russia must remove its vehicles and its personnel from the territory of Ukraine immediately. Failure to do so will result in additional costs and isolation,” he said.
Kirby said the U.S. is consulting with international partners to determine the next steps. He also expressed concern about what he said were more than 10,000 Russian troops along the border with Ukraine.
“They are, as I’ve described before, combined arms capable: armor, artillery, infantry, air defense. They’re very ready. They’re very capable. They’re very mobile. And they continue to do nothing but just increase the tension on the other side with Ukraine,” he said.
Kirby said Russia is continuing to support the separatists in Ukraine with heavy weapons, including tanks, artillery and air defense systems.
Watch related video report by VOA's Zlatica Hoke
The first trucks in a Russian convoy reportedly carrying humanitarian aid crossed Friday into Ukraine and arrived in the besieged city of Luhansk, officials said, in a dangerously provocative move that Kyiv had warned would be tantamount to invasion.
The arrival of the convoy, which had been stalled across the border in Russia for weeks while officials negotiated terms for allowing it to enter, put Ukraine and Russia on the verge of all-out war.
The first of the 260 trucks began crossing the border earlier Friday and Russian and Western news reports said some of the trucks had reached Luhansk by late afternoon.
Kyiv and many Western officials had suspected that Moscow could use the convoy as a pretext for an invasion. Russia's Foreign Ministry said in a statement Friday that all excuses for the convoys' delay had been exhausted.
NATO, meanwhile, warned that Russian artillery was being used against Ukrainian troops, from across the border and from within Ukraine and large numbers of tanks, armored personnel carriers, and artillery were being shipped to rebels.
In New York, Russia's United Nations ambassador, Vitaly Churkin, challenged the claims of a Russian military presence in Ukrainian territory. "They need to provide proof," he said.
President Petro Poroshenko also called the move a violation of international law, while the chief of Ukraine’s lead security agency, Valentyn Nalivaychenko, condemned Moscow for ordering the trucks into Ukrainian territory before they were inspected and approved.
The Red Cross said it was not escorting the convoy because it had not received security guarantees. The organization said its team in Luhansk reported heavy shelling overnight.
"The Russian aid convoy is moving into Ukraine, but we are not escorting it due to the volatile security situation,'' the Red Cross said in a posting on Twitter.
UN Secretary-General statement
A spokesman for Secretary-General Ban Ki-moon said Ban "follows with deep concern reports that a Russian aid convoy has crossed the border into Ukraine without the permission of the Ukrainian authorities. While recognising the deteriorating humanitarian situation, any unilateral action has the potential of exacerbating an already dangerous situation in eastern Ukraine."
The Secretary-General is urging all sides, especially Ukraine and the Russian Federation, to continue to work together, along with the international community, to ensure that humanitarian assistance reaches the most affected areas. He reiterates that all sides should continue to exercise maximum restraint and avoid escalation.
The statement went on to say Ban is encouraged by the announcement from Poroshenko that Ukraine "will do everything possible to prevent more serious consequences as a result of the convoy moving into Ukrainian territory."
In Washington, Benjamin Rhodes, the White House deputy national security adviser, said Russia must remove the convoy from Ukrainian territory and said the United States would bring the subject for discussion at the United Nations Security Council.
"If Russia really wants to ease the humanitarian situation in eastern Ukraine, it could do so today by halting its supply of weapons, equipment, and fighters to its proxies," National Security Council spokeswoman Caitlin Hayden said in a strongly worded statement. "We condemn this action by Russia, for which it will bear additional consequences. "
Defense Department spokesman Rear Adm. John Kirby earlier said that the estimated 10,000 Russian troops stationed at the Ukrainian border remain "very ready, very capable, and very mobile."
NATO warns of Russian artillery
The European Union’s foreign policy chief, Catherine Ashton, urged Russia to reverse its decision. NATO chief Anders Fogh Rasmussen accused Moscow of escalating the crisis.
"It can only deepen the crisis in the region, which Russia itself has created and has continued to fuel," he said in a statement.
Rasmussen also said that NATO had also seen transfers of large quantities of advanced weapons, including tanks, armored personnel carriers, and artillery to separatists.
"Moreover, NATO is observing an alarming build-up of Russian ground and air forces in the vicinity of Ukraine," Rasmussen said.
For weeks, Moscow had insisted that Luhansk was suffering a humanitarian catastrophe. The Ukrainian military had pounded rebel positions in and around the city, and earlier this week, had even managed to enter and raise a Ukrainian flag over one administration building.
The trucks in the convoy were reported to be carrying food, water, generators, and sleeping bags, but Western reporters who inspected the trucks said many were only partially full.
On Thursday, Ukrainian officials said border guards had begun checking convoy but it was unclear how many trucks they managed to inspect.
Nalivaychenko on Friday alleged that the convoy was actually made up of military vehicles driven by members of the Russian military, using fake documents, and that the drivers were trained to operate military vehicles, tanks and artillery.
Earlier in the week, Ukrainian troops reclaimed control of the nearby town of Ilovaysk, after heavy fighting with separatists. The town is strategically important because of its roads and rail line.Troops have also surrounded much of Donetsk, the largest city in the region.
In an interview televised Friday, Prime Minister Arseniy Yatseniuk said Russia's actions showed that it could not accept Ukraine's moves toward integration with Europe.
“Nothing will stop us. We have taken that decision. We are part of Europe. That is where we are going,'' he said.
Poroshenko had been set to attend a meeting next week with his Russian counterpart and others in the Belarusian capital Minsk.
If it takes place, the August 26 meeting would place the two leaders in the same room for the first time since a brief encounter in France in June.
Over 2,000 soldiers, rebels, and civilians have been killed since the fighting broke out in April.
Information from Reuters and The Associated Press was used in this report.