[KIEV] Ukraine's military on Thursday said days of unceasing artillery strikes by pro-Russian insurgents had forced its soldiers to abandon a shattered airport that had become the symbolic prize of the nine-month war.
Defence officials said fighting around the ruins of the Donetsk air hub - once one of eastern Europe's busiest and most modern - continued despite the deaths of six Ukrainian troops and capture of 20 more by separatists overnight.
But Ukraine's small paratrooper force had to pull out of the main airport building after a 242-day siege that some media compared to the horrific World War II Battle of Stalingrad.
"Yesterday evening we made the decision to leave the new terminal," military spokesman Vladyslav Seleznyov said.
A Ukrainian official in charge of organising prisoner swaps said victorious rebel commanders intended to send some of the detained soldiers to Russia for further questioning.
Kiev reported making its painful decision to retreat just minutes after at 13 civilians lost their lives when an artillery shell hit a trolleybus near Donetsk city centre.
Ukraine also said 10 soldiers were among the nearly 50 people killed the bloodiest 24-hour spell of fighting since the signing of a largely ineffective September truce.
The rebel capital in eastern Ukraine has witnessed a dramatic escalation of attacks in recent days, bringing to more than 5,000 the number of people known to have died in one of Europe's most irreconcilable and diplomatically explosive conflicts in decades.
The United States on Wednesday branded the rebels' surge and Moscow's latest comments in support of a ceasefire little more than a "Russian occupation plan" for its western neighbour.
"We lost the airport," Ukraine's all-volunteer Azov regiment commander Andriy Biletskiy wrote on Facebook.
"After this defeat, we cannot expect (Russia) to give us good terms for any future ceasefire."
The Sergei Prokofiev International Airport was rebuilt at a cost of nearly US$1 billion to host football fans arriving for matches during the Euro 2012 championship.
The gleaming structure was designed to showcase Ukraine's post-Soviet emergence as a democratic and thriving state.
But it soon became a reflection of the strife tearing apart its Russian and Ukrainian speakers - as well as the bitter East-West wrangle over the allegiance of a country sandwiched between Kremlin and NATO troops.
The airport was first attacked by the rebels just days after the presidential election of Petro Poroshenko - a pro-Western tycoon who vowed to cement Ukraine's ties with Europe and the United States.
Ukrainian media began referring to soldiers hanging on to the hub as "cyborgs" because of their seeming ability to withstand nonstop assaults from heavily-armed separatists with limited logistical support from Kiev.
Poroshenko's top security adviser said Kiev was not yet ready to fully cede the airport's grounds to the gunmen - despite Russia's diplomatic pressure to do so - because it remained a neutral site under the September agreements.
"Donetsk airport has been and remains a part of the front line," presidential adviser Yuriy Biryukov wrote on Facebook.
The Ukranian spokesman for the eastern campaign said Kiev's forces were now in control of just a few structures around the vast airport site.
"We are continuing to hold on to the fire department building, the air traffic control tower and an area around the runway, which is also completely destroyed," Andriy Lysenko told reporters.
But the defence ministry later said the buildings listed by Lysenko have been "demolished" by shelling.
"The Ukrainian armed forces have taken up advantageous positions near the airport and are using artillery to attack enemy forces inside the airport and on its outskirts," the ministry said.