The Kremlin says Russian President Vladimir Putin spoke by phone Tuesday with his Ukrainian counterpart Petro Poroshenko about a possible cease-fire in southeastern Ukraine.
No details were released, but Kremlin spokesman Dmitri Peskov said Putin also voiced concern over the deaths Tuesday of two Russian state journalists near the Ukrainian city of Luhansk. Peskov said Ukraine has promised to investigate the deaths. Regional news reports say the journalists died when their car was hit by mortar fire near the rebel-held city.
The top-level discussion is only the second known direct contact between leaders of the two countries since Russia annexed Ukraine's Crimean peninsula in March.
The call followed an explosion in central Ukraine's Poltava region Tuesday hit a section of the largest transit pipeline for Russian natural gas to western Europe, in what one Ukrainian official said may have been a terrorist act.
Ukraine's Interior Minister Arsen Avakov said several theories for the cause of the explosion were being considered, the main one being that it was "a terrorist act." He said local residents heard two loud blasts just before the section of pipeline burst into flames, suggesting a "deliberate" act.
Local officials quoted eyewitnesses as saying they saw flames from the fire reaching up to 200 meters. No one was hurt in the incident.
Avakov said Ukrainian authorities last month thwarted two attempted attacks against Ukraine's gas pipeline system in western Ukraine.
The Reuters news agency quoted a source at Gazprom, Russia's state-run natural gas company, as saying that blast had not disrupted the flow of gas thanks to a "parallel pipeline."
Tuesday's blast took place hundreds of kilometers away from eastern Ukraine, where pro-Russian separatists have been fighting Ukrainian government forces and have declared two so-called "people's republics."
On Monday, Russia cut off gas supplies to Ukraine in a pricing dispute.
The pipeline explosion took place amid reports of continuing violence in eastern Ukraine.
Ukrainian media reported Tuesday that separatists were using heavy artillery to shell Ukrainian army units in the Luhansk region.
A Russian state television reporter (Igor Kornelyuk) was killed Tuesday in the Luhansk fighting, apparently as the result of mortar fire. His sound engineer was reported missing.
Russia's Foreign Ministry said in a statement that the reporter's death proved "the criminal nature of the forces who unleashed the punitive operation in eastern Ukraine."
Meanwhile, Ukraine's parliament on Tuesday appealed to foreign journalist organizations to counter what it called "acts of media provocation" and unverified information being disseminated by the Russian press.
The appeal, which was addressed to groups including Reporters Without Borders and the International Federation of Journalists, accused Russia of spreading "false, incomplete and biased information about Ukraine" as part of a "coordinated and targeted information war."