The detainee acknowledged being on active military service in Russia during questioning.

Another man, detained along with the Russian officers identified himself as a pro-Russian militant fighter, according to Ukraine Today.

The truck was supposedly moving from another separatist-controlled town of Olenivka as it was stopped following warning shots from Ukrainian border guards.

Russian military officials did not comment immediately, while the self-styled “ministry of defense” of the Russian proxies in Donetsk rejected Ukraine's claim, saying it "provokes irony".

Detention of a Russian officer will add up to Ukraine's charges that Russia is directly involved in military conflict in Ukrainian Donbas, failing to fulfill the truce signed in Minsk this February.

See’s video section for more of the latest news from Ukraine in video from Ukraine Today, Ukraine’s 24-hour English-language news channel.