The Red Cross will lead an international humanitarian aid operation with Russia and the European Union into the rebel-held city of Luhansk — a plan that Ukraine says has the backing of U.S. President Barack Obama.
The Kremlin earlier announced that it was dispatching the humanitarian convoy into eastern Ukraine.
Ukraine had previously objected to Russia sending any aid into the region, and the West had strongly warned Russia that any attempt to send its military personnel into Ukraine under the guise of humanitarian assistance would be seen as an invasion.
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In the last week, Ukrainian government forces have been closing in on the few remaining pro-Russian rebel strongholds in eastern Ukraine, including surrounding Donetsk, the largest rebel-held city. Hundreds of thousands have been fleeing the fighting.
Shortly after the Kremlin statement, Ukrainian President Petro Poroshenko spoke on the phone with Obama, according to their offices.
Ukraine and the West have accused Russia of supplying heavy weapons and other equipment to the rebels in eastern Ukraine, a charge that Russia denies.
The Kremlin statement came after a telephone call between Russian President Vladimir Putin and European Commission chief Jose Manuel Barroso. It didn't say when the convoy would leave or provide other details.
Barroso's office said he warned Russia "against any unilateral military actions in Ukraine, under any pretext, including humanitarian."
Russian Foreign Minister Sergey Lavrov said Russia has agreed on details of a humanitarian mission with the Ukrainian leadership.
"I hope that our Western partners will not put a spanner in the works," he said.
Lavrov said that the Ukrainian military action in the east looks like an attempt to "raze it to the ground to force the Russians to leave and settle it with others who would have a different attitude to our nations' history, culture, friendship and links that have existed for centuries."
Barroso also talked to Poroshenko, emphasizing "the EU's readiness to increase its support to the Ukrainian government-led humanitarian response efforts as well as to international humanitarian organizations."
Dangerous inmates escape
Earlier Monday, rockets slammed into a high-security prison in Donetsk, igniting a riot that allowed more than 100 prisoners to flee, authorities said.
Donetsk city council spokesman Maxim Rovinsky said a direct rocket hit killed at least one inmate and left three others severely wounded. In the chaos, he said 106 prisoners escaped, included some jailed for murder, robbery and rape.
Many of those in Russian-speaking eastern Ukraine distrust the new central government in Kyiv, which came to power after the February ouster of former President Viktor Yanukovych, whose power base was in eastern Ukraine.
Fighting began a month after Russia annexed Ukraine's peninsula of Crimea in March.