Illegal armed groups have intensified air reconnaissance using unmanned aerial vehicles in the eastern regions of Ukraine, and on the administrative border with Crimea, anti-terrorist operation spokesman Andriy Lysenko has said.

"The enemy has significantly intensified air reconnaissance over the past 24 hours," he said at a briefing on Thursday.

He said that Ukrainian border guards had recorded the use of 19 UAVs in different districts of Donetsk and Luhansk regions, as well as on the administrative border with Crimea.

He also said that residents of the militant-occupied territories complained that separatists were involved in fraud concerning Russian humanitarian aid.

"In Luhansk region the militants invented a new kind of extortion from local entrepreneurs. They force all bus operating companies that travel outside the occupied territories to pay 20% fees from profit," Lysenko said.

In addition, he said militants from the self-proclaimed "Donetsk People's Republic" are trying to increase their ranks by mobilizing local teenagers aged 16-18.