Russian President Vladimir Putin has said he will respect the choice of the Ukrainian people in this weekend’s presidential vote but that ousted ex-leader Viktor Yanukovych technically remained in power.

"We understand that the people of Ukraine want their country to emerge from this crisis. We will treat their choice with respect," Mr Putin told an economic forum.

"It would have been better to hold a referendum and adopt a new constitution. Under the current constitution Yanukovych is still in power."

Mt Putin's comments came the same day as at least five people were reported to have been killed in fighting between pro-Russian militiamen and Ukrainian forces near the eastern city of Donetsk.

An AFP photographer said he saw five bodies near the village of Karlivka northwest of Donetsk, four of them apparently rebels and the fifth possibly from a volunteer force attached to the military.

Fighting in the east has witnessed a bloody resurgence ahead of Sunday's presidential election that the pro-Russian insurgents have vowed to disrupt.

Yesterday, attacks by separatist gunmen in the rebel-held regions of Donetsk and Lugansk killed a total of 18 soldiers, according to a new toll provided by a military spokesman.

It was by far the heaviest loss for the Ukrainian military since it launched what it calls an "anti-terrorist" operation against the rebels in mid-April.