(USA TODAY) -- A Ukrainian general and 13 servicemen were killed Thursday when pro-Russian rebels shot down a military helicopter near Slovyansk in the restive eastern regions of Ukraine, according to outgoing president Oleksandr Turchynov.
The interim president told Ukraine's parliament that the chopper carrying Gen. Volodymyr Kultchitsky was brought down by anti-aircraft fire operated by insurgents, Interfax Ukraine reports.
Slovyansk, which is located about 100 miles west of the Russian border on the Donetsk region, has been at the center of major clashes in recent weeks between Ukrainian troops and separatists.
"Recently I received information that the terrorists shot down our helicopter, due to Russian man-portable SAM weapon, with 13 servicemen, including General Kulchytsky on board, who were killed," Turchynov told lawmakers.
The chopper was apparently hit after it had dropped off troops to a military base in the area.
Turchynov has served as interim president following the ouster of Viktor Yanukovych in February. A new president, Petro Poroshenko, a wealthy candy manufacturer, was elected on Sunday and has vowed to root out the rebel forces that have seized government building and claimed independence for the region.
In a separate development, an insurgent leader in eastern Ukraine said Thursday that his fighters are holding four monitors from the Organization for Security and Cooperation in Europe and promised that they would be released soon.
Vyacheslav Ponomarev, the self-proclaimed "people's mayor" of Slovyansk, told The Associated Press that the monitors — who are from Turkey, Switzerland, Estonia and Denmark — are safe.
"I addressed the OSCE mission to warn them that their people should not over the coming week travel in areas under our control. And they decided to show up anyway," Ponomarev said.
"We will deal with this and then release them," he said, without setting any specific time frame.
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 OSCE monitors have been deployed to Ukraine to monitor security situation following Russia's annexation of Crimea and a pro-Russia separatist insurgency that has engulfed regions in eastern Ukraine. They also observed Sunday's presidential vote, won by billionaire candy magnate Petro Poroshenko.
In the most ferocious battle yet, rebels in Donetsk tried to take control of its airport Monday but were repelled by Ukrainian forces using combat jets and helicopter gunships. Dozens of men were killed and some morgues were overflowing Tuesday. Some insurgent leaders said up to 100 fighters may have been killed.
The mood in Donetsk was calm Thursday, although many businesses have stopped opening their doors over fear of renewed fighting.
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.
Putin has supported an OSCE peace plan that calls for ending hostilities and launching a political dialogue. Russia also said it would be ready to work with new leader Poroshenko, but strongly urged the Ukrainian government to end its military operation in the east.
Contributing: Associated Press