A convoy of what appeared to be Russian military vehicles has entered a base near Crimea's capital, Simferopol.
News agency reporters who videotaped the convoy Saturday say it included gasoline tankers, eight armored vehicles and two ambulances. The convoy drove onto a military airfield flying a Russian flag.
Russia denies it has troops in Crimea beyond those regularly stationed with its Black Sea fleet based in Crimea.
Witnesses say although the soldiers have no insignia identifying them, they are clearly Russian.
Earlier, witnesses said warning shots were fired when pro-Russian forces refused to let a monitoring team from the Organization for Security and Cooperation in Europe enter Crimea. It was the third day in a row that a team of observers had been refused entry to the area.
Acting Ukrainian Foreign Minister Andrii Deshchytsia Saturday called for a diplomatic resolution and a peaceful end to the crisis. He said Ukraine is open to any possibility that leads to "concrete results," but emphasized "Crimea is and will be Ukrainian territory."
Unease in Crimea continues even though Ukraine's interim president, Oleksandr Turchynov, signed a decree Friday canceling a March 16 referendum on Crimea joining Russia.
Interim Ukrainian Prime Minister Arseniy Yatsenyuk says "no one in the civilized world" will recognize the referendum's results, but local authorities in Crimea say the ballot will go forward.
The speaker of Russia's upper house of parliament, Valentina Matviyenko, has said Russian lawmakers will support Crimea's decision if the Ukrainian region decides to join Russia.