* Graphic on region link.reuters.com/cux42w
KIEV, Aug 4 (Reuters) - Five government soldiers were killed and 15 wounded over the last 24 hours in fighting in eastern Ukraine where Kiev forces recaptured an important railway hub from pro-Russian rebels, a security official in Kiev said on Monday.
Kiev has intensified its campaign against the Moscow-backed separatists and made steady gains on the ground since a Malaysian airliner was downed over rebel-held territory on July 17, killing all 298 people on board.
Government troops have now all but encircled the rebels' second-largest stronghold of Luhansk and rebels declared a "state of siege" in Donetsk, the largest city they hold.
"Units taking part in the anti-terrorist operation yesterday took the town of Yasynuvata, which is an important hub of the region's railway system," Andriy Lysenko, a spokesman for Kiev's military operation in the east, told a briefing.
Separatists seized the Yasynuvata railway control centre in May as their rebellion spilled over eastern Ukraine. It sits just north of Donetsk nearby a main road leading to Luhansk.
Fighting left Luhansk without electricity or running water and mobile network was also down, local officials said on Monday.
Lysenko also said a group of Ukrainian soldiers and border guards, who have been blocked between the Russian border to the east and pro-Russian rebel position in the west for more than three weeks, crossed into Russia in the early hours on Monday.
"Today at 4:30 a planned operation took place to unblock a Ukrainian military unit nearby Chervonopartyzansk. A large part (of the unit) successfully ... reached a safe place," Lysenko said.
"Part of the soldiers (group) went into the Russian territory," he said, adding Kiev was now trying to negotiate their return. He refused to say how many servicemen had crossed the border but the wife of one of them, speaking on Ukraine's 112 TV channel, put the number at around 200.
The OSCE, which is fascilitating the work of international experts on the Malaysian Boeing crash site, said on Twitter more than a hundred experts reached the area with detector dogs on Monday but were not starting recovery and investigative work.
"(They) are remaining stationary pending further security assessments," the Organization for Security and Cooperation in Europe said.
A large group of international experts has worked on the site since Friday after fighting in the area had stalled efforts to reach the site for several days before that.
Reporting by Natalia Zinets and Pavel Polityuk, Writing by Gabriela Baczynska; Editing by Richard Balmforth/Jeremy Gaunt