MOSCOW (AFP) - A senior Russian lawmaker said military units are occupying positions in Crimea in case of armed attack from Kiev, in the first apparent admission by Moscow that its forces have occupied the Ukrainian region in a military operation.

President Vladimir Putin has insisted that the uniformed gunmen who are openly patrolling Crimea with military hardware and weapons are local self-defence brigades and even suggested they bought their uniforms in a shop.

"Now there are some military units there who are occupying positions in case there is such resistance, armed aggression, armed expansion from Kiev," the head of the State Duma's committee for relations with ex-Soviet states, Mr Leonid Slutsky, told Echo of Moscow radio station in a late-night interview Wednesday.

"It is not a large-scale military operation," added the lawmaker, who often speaks for the parliament on Ukraine.

"When bandit units - God forbid - surge into the southeast of Ukraine, particularly to Crimea, you understand that it will be difficult to oppose that instantly. We're not magicians."

He said that troops could be required if Sunday's referendum on Crimea's joining Russia prompted armed intervention from Kiev, which he said was likely.

"Therefore in this case, yes, some military units are occupying positions here, since such an incursion unfortunately especially in the days when the referendum is held is highly likely," he said.

But he said troops would only act in the case of an armed attack from Kiev.

"Troops will go in only, I want to emphasise, if some bandit units surge... from Kiev to Crimea to spill blood. Not in any other case... I think if there will not be such units, there will not be any operations."

"There will not be a war in any situation," Mr Slutsky said.