* Kiev, West say Russia propping up separatist revolt
* EU ministers discuss new sanctions on Moscow
* Nearly 2,600 civilians, fighters killed - U.N.
KIEV, Aug 30 (Reuters) - A group of pro-Ukrainian fighters broke out of encirclement by Russian-backed separatists near the eastern city of Donetsk early on Saturday, Ukraine's interior minister said, but other reports suggested many were still trapped.
Fighting has intensified in areas near the small town of Ilovaysk and further south along the Sea of Azov coast where separatists are now threatening the port city of Mariupol.
Kiev and Western countries say the reversal is the result of the arrival of armoured columns of Russian troops, sent by Russian President Vladimir Putin to prop up the five-month-old separatist revolt in eastern Ukraine which had been near collapse.
A senior U.N. human rights official said on Friday nearly 2,600 civilians, Ukrainian government forces and rebels have been killed in a conflict which has led to the biggest Russia-West crisis since the Cold War.
EU foreign ministers were due to meet in Brussels on Saturday to discuss the possibility of imposing new sanctions on Moscow over the crisis.
Against a background of reports - unconfirmed by Kiev military - that Ukrainian forces had been surrounded near Ilovaysk, Interior Minister Arsen Avakov said on Saturday that a group of pro-Ukrainian fighters had broken out of encirclement after the National Guard formed a protective wedge.
They included 28 fighters from pro-government militia units as well as a group of servicemen, he said. "We didn't hold the line for nothing through the night!", Avakov wrote on his Facebook page. "Now we are waiting for the rest of the guys."
The leader of another pro-government militia, called the Donbass battalion, said however that many of his forces were surrounded near the small town of Starobesheve and he wanted an agreement with the rebels to provide a safe route out.
Putin said on Friday the pro-Russian separatists had managed to halt Kiev's offensive on the rebels - which Moscow portrays as the root cause of the conflict - and proposed that the rebels allow Ukrainian troops to retreat.
Moscow denies direct involvement by the Russian military.
The rebels have said they will accept Putin's proposal provided Kiev government forces turn over weapons and armour.
Semen Semenchenko, leader of the Donbass battalion, said he was waiting for a high-level deal to come together that would secure a safe exit for his men. "We are telephoning our guys to keep their spirits up," Semenchenko said on his Facebook page.
There was no word on any such agreement from the side of Ukrainian President Poroshenko who on Saturday was in Brussels. But a Kiev government source, who did not wish to be named, said: "We will do all we can to get our men out of there."
Up to 800 Ukrainian government forces have been killed in the conflict so far. Ukraine's military information service said another Ukrainian warplane, an SU-25, was shot down on Friday. The pilot ejected safely and had been found, it added.
(Reporting by Pavel Polityuk; Writing by Richard Balmforth)