A passenger bus came under heavy fire in eastern Ukraine today killing at least ten people, Ukrainian authorities said.
Fighting intensified around the international airport in the city of Donetsk as separatists tried to oust government forces.
The latest violence flared after Russia, Ukraine, France and Germany scrapped plans for a summit in Kazakhstan this week, because of the failure to implement a four-month-old ceasefire agreement.
A senior official from the Organisation for Security and Cooperation (OSCE) in Europe called for maximum restraint from all sides in the Ukraine conflict, which has killed more than 4,700 people since last April.
"Over the past 24 hours the situation has significantly deteriorated, especially near the Donetsk airport.
More civilian casualties have been reported elsewhere," said Ertugrul Apakan, head of the OSCE special monitoring mission in Ukraine.
The war between Ukrainian forces and pro-Russian rebels broke out soon after Russia annexed Crimea last year, creating the worst crisis in East-West relations since the Cold War.
Western governments accuse Russia of backing the separatists, including by sending in troops, which it denies.
Photographs showed the bus peppered by holes, as were seats inside it.
A long trail of blood marked the road beside it near the town of Volnovakha.
"Ten people have been killed and at least 13 are wounded," a regional Ukrainian administration spokesman said.
He said the bus was attacked by rebels using Grad rocket launchers while it was carrying civilians through a government checkpoint.
Separatists denied responsibility and said the bus had been attacked by small arms fire rather than a missile or shell.
