(Reuters) - Shelling hit a passenger bus in eastern Ukraine on Tuesday, killing at least 10 people, and fighting intensified around the international airport in the city of Donetsk as separatists tried to oust government forces.
The bus attack near the town of Volnovakha south of Donetsk, which is the heart of a nine-month-old separatist conflict, further deflated peace hopes after talks between Russia, Ukraine, France and Germany ended without notable progress on Monday. Pro-Russian rebels seized parts of eastern Ukraine after Kiev's Moscow-backed president was toppled by popular unrest.
"Ten people have been killed and at least 13 are wounded," a regional Ukrainian administration spokesman said, adding that the bus came under attack from rebels holding the town of Dokuchaevska further to the north.
He said the bus was carrying civilians from the coastal town of Mariupol through a government checkpoint. Separatist leaders denied responsibility for the shelling, saying the incident occurred at a rebel checkpoint.
Photographs showed the bus peppered by holes, as were seats inside it. A long trail of blood marked the road beside it.
Fighting intensified around Donetsk airport as prospects faded for a new big-power effort to end the conflict, which has cost more than 4,700 lives and stoked East-West tension recalling the Cold War over Western accusations of Russian military backing for the rebels. Moscow denies this.
Ukraine, Russia, Germany and France scrapped plans to hold a summit in Kazakhstan later this week because of the failure to implement a four-month-old ceasefire agreement fully and there was no sign of when it might be rescheduled.
Reports from Donetsk said a significant part of the airport's multi-story control tower - already a wrecked hulk with cabling and concrete dangling from it after months of shelling - had been destroyed.
After a night of attacks from separatists using Grad missile launchers, the rebels began firing from tanks on the airport's new terminal, which was still being held by Ukrainian government forces, the Kiev military said in a statement.
"The Russian military and the terrorists have deliberately chosen the tactic of escalation of tension," military spokesman Andriy Lysenko told journalists. One Ukrainian soldier had been killed and 10 wounded in overnight fighting.
SYMBOLIC VALUE
The Sergei Prokofiev airport complex, opened to great fanfare by the now ousted president Viktor Yanukovich to mark the Euro 2012 soccer championship, has progressively disintegrated under months of fire and is now a shattered hulk.
But though it has not functioned as an airport since the onset of hostilities last April, with its runways cratered by shell holes, it has symbolic value for both sides and government forces have repelled repeated rebel attempts to dislodge them.
"After nine months of confrontation in Donetsk airport the (separatist) fighters have succeeded in bringing down the top (of the control tower) to the fifth floor," Lysenko said.
In the capital Kiev, a parliamentary deputy said government forces had been given an ultimatum by the rebels to pull out of the airport by 5 p.m. (1000 ET) "or face destruction".
This could not be confirmed from the separatist side.
The Russian, German and French government leaders had been invited to talks on Thursday in the Kazakh capital Astana by Ukrainian President Petro Poroshenko.
But the four countries' foreign ministers said after meeting in Berlin that the failure to implement the ceasefire deal and the need to agree on how to deliver aid and free prisoners meant "further work needs to be done" before a summit is held.
(Reporting by Stephen Brown in Berlin, Elizabeth Piper in Moscow, Pavel Polityuk and Natalia Zinets in Kiev; Writing by Richard Balmforth; Editing by Mark Heinrich)
