DONETSK, Ukraine: Thirteen civilians died when shells hit a trolleybus Thursday in Ukraine's rebel bastion Donetsk as clashes forced Kiev to abandon its dogged defense of the city's airport in one of the deadliest days of the nine-month war.
The shelling of the bus and reports of at least 34 Ukrainian soldiers killed over the past day came only hours after peace talks in Berlin called for a cease-fire.
With intensifying clashes rocking Donetsk airport in recent days, Ukraine's military said early Thursday that its troops had abandoned the main part of the site.
The airport had become the symbolic prize of the conflict, with the army and pro-Russian rebels continuously battling for control of the devastated site.
"Yesterday evening we made the decision to leave the new terminal," military spokesman Vladyslav Seleznyov said in reference to the main airport building that had been held by Kiev forces since late May.
The trolleybus shelling was among the bloodiest incidents involving civilians in recent months in a conflict that has killed more than 5,000 people since April. Around a dozen people were also wounded.
Stunned Donetsk residents gathered around the shredded remains of the bus, with several bloodied bodies of elderly victims still sprawled in their seats hours after the attack and local militias cautiously inspecting the damage.
"Twelve people were killed in the trolleybus and another who was in a car that was passing nearby," said an official with the emergency services in the city.
Russia's government-controled television immediately blamed the attack on Kiev's forces, while Ukraine said the rebels were responsible.
The strike occurred just south of Donetsk's city center, with concerns having been raised over shelling that has at times moved closer in from the airport northwest of the city, putting civilians in increasing danger.
In a separate incident Wednesday night, shelling in a neighborhood near the airport hit another bus and killed one person, city official Ivan Prikhodko told AFP.
Thursday's violence came hours after the foreign ministers of Russia, Ukraine, Germany and France ended a crisis meeting in Berlin with a joint call to cease hostilities, but no breakthrough agreement to stop the bloodshed.
The talks had been held against the unpromising backdrop of fresh clashes and after Ukraine's president accused Moscow of fuelling the war with fresh troops and tanks.
The four top diplomats in their statement could agree to "call on all sides involved to cease hostilities and to withdraw heavy weapons" back from a demarcation line agreed in the widely flouted September truce signed in Minsk.
"I'm not going to say we saw a breakthrough, but I think we saw tangible progress today," said the host, German Foreign Minister Frank-Walter Steinmeier.
Steinmeier said the main achievement was that all sides had agreed that the demarcation line agreed in the Minsk pact would form the basis for the pull-back of heavy arms on both sides.
The talks had "tested the patience of all participants," he said after meeting his Russian counterpart Sergei Lavrov, who left the talks first, as well as Ukraine's Pavlo Klimkin and Laurent Fabius of France.
The ministers said that before a hoped-for Kazakhstan peace summit could be held, there must be tangible progress on implementing the Minsk agreements, including an effective cease-fire and agreed ways to deliver humanitarian aid to the region.
U.S. Secretary of State John Kerry accused the rebels of attempting "a blatant land grab," while Washington's U.N. envoy Samantha Power accusing Russia of pursuing an "occupation plan" in the east.
Ukrainian President Petro Poroshenko, speaking Wednesday at the World Economic Forum in Davos, said the upsurge in fighting after a nearly month-long lull was prompted by a new surge of Russian forces and weapons.
"We have more than 9,000 troops of the Russian Federation on my territory, including more than 500 tanks and heavy artillery and armed personnel carriers," the pro-Western leader said.
Moscow strongly denies supporting the insurgents despite NATO satellite imagery purporting to show its forces' presence in Ukraine.