A Ukrainian military helicopter has been shot down in Slovyansk, killing 14 people including an army general, as rebels and government forces continued fierce battles in the country's east.
The acting Ukraine president, Oleksandr Turchynov, told parliament on Thursday: "I have just received information that terrorists using Russian anti-aircraft missiles shot down our helicopte. It had been ferrying servicemen for a change of
He said General Serhiy Kulchytskiy was among the dead, according to the Interfax news agency, which earlier gave the wrong first name for the general.
The Interfax news agency said Kulchytskiy had once served in the Soviet army and was in charge of combat training for Ukraine's National Guard.
A separatist spokesman had earlier told Russian news agencies that the militants had downed a Ukrainian army helicopter in a fierce battle that was still raging on the southern outskirts of the rebel-controlled city.
The unnamed spokesman said that "as a result of active military activities, several houses belonging to civilians caught fire".
The attack came as separatists in Donetsk began holding funerals for dozens of fighters killed in the battle for the city's airport on Monday.
More than 35 fighters were killed on Monday during the prolonged battle between the rebels and the Ukrainian army. The clashes involved combat jets and helicopter gunships, and rebel leaders say up to 100 fighters had died.
The self-proclaimed prime minister of the Donetsk People's Republic, Aleksander Boroday, told families of the dead that he and his supporters were "prepared for more fighting".
Speaking in front of relatives gathered at the Kalininsky Hospital mortuary, he said he hoped he would not have to request "more assistance" from Russia, Al Jazeera's John Wendle in Donetsk reported.
Kiev says Russia is sending troops to fight with separatists. Moscow denies the accusations, saying it has no influence over rebels.
Meanwhile, a rebel leader in Slovyansk said his fighters were holding four observers from the Organisation for Security and Cooperation in Europe and promised that they would be released imminently.
Vyacheslav Ponomarev, the self-proclaimed "people's mayor'' of Slovyansk, said the monitors who were from Turkey, Switzerland, Estonia and Denmark were safe.
The OSCE said it had lost contact with one of its four-man monitoring teams in Donetsk on Monday evening.
Rebels have previously kidnapped military observers working under the auspices of the OSCE.
The rebels have declared the Donetsk and Luhansk regions independent of Ukraine.
They have pleaded to join Russia, but President Vladimir Putin has ignored their appeal in an apparent bid to de-escalate tensions with the West and avoid a new round of Western sanctions.
Ukraine's president-elect, Petro Poroshenko, has promised to negotiate with people in the east, where rebels have fought government troops for a month-and-half.
Moscow said it would be ready to work with Poroshenko, but strongly urged the Ukrainian government to end its military operation in the east.