From staff and wire reports

Three Ukrainian commando dolphins trained to search for mines, attack divers and plant explosives have escaped from their handler in the Crimea, Russia's RIA Novosti news agency reported Tuesday.

The news agency, citing the Ukrainian media, said only two of five military-trained "killer" dolphins returned to their base in the port city of Sevastopol after recent exercises.

RIA Novosti said the Ukrainian defense ministry denied the reports of killer dolphins going AWOL, but also even refused to confirm the existence of such a program.

Dolphins were trained for commando missions at Sevastopol for the Soviet navy as far back as 1973, but Ukraine took over the unit after the Soviet breakup and the splitting of the Black Sea fleet into the Ukrainian and Russian fleets.

To keep the unit intact, the dolphins were trained for civilian tasks such as working with disabled children.

A military source in Sevastopol told RIA Novosti last year, however, that the Ukrainian navy had restarted training dolphins for commando operations, such as attacking enemy combat swimmers using special knives or pistols fixed to their heads.

They were also being trained to plant explosives, carried on their heads, on enemy ships, the unidentified source is quoted as saying.

Even in the past, training could go awry at certain times of the year, a former Soviet naval trainer told the news agency, and may account for the latest defections.

"If a male dolphin saw a female dolphin during the mating season, then he would immediately set off after her, Yury Plyachenko, a former Soviet naval anti-sabotage officer told RIA Novosti."But they came back in a week or so."

CBS Seattle reports that other militaries, including the U.S. Navy, also usedolphins, but that the U.S. trains them not for attack but for intelligence gathering. CBS reports dolphins were used in the Iraq War.

Contributing: Doug Stanglin, USA TODAY