Putin's statement came several hours after Ukraine accused Russia of entering its territory with tanks, artillery and troops, and Western powers accused Moscow of lying about its role and dangerously escalating the conflict.
NATO said at least 1,000 Russian troops are in Ukraine and later released what it said were satellite photos of Russian self-propelled artillery units moving last week.
"I'm calling on insurgents to open a humanitarian corridor for Ukrainian troops who were surrounded in order to avoid senseless deaths," Putin said in the statement published on the Kremlin's web-site in the early hours today.
Putin's statement could be referring to Ukrainian troops who have been trapped outside the strategic town of Ilovaysk, east of Donetsk, for nearly a week now. Protesters rallied outside the Ukrainian General Staff yesterday, demanding reinforcements and heavy weaponry for the troops outside Ilovaysk, most of whom are volunteers.
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A top rebel leader in the rebel stronghold of Donetsk promptly reacted to Putin's appeal but said the Ukrainian troops would have to lay down the arms before they were allowed to go.
Two columns of tanks and other equipment entered southeastern Ukraine at midday yesterday, following heavy shelling of the area from Russia that forced overmatched Ukrainian border guards to flee, according to Col Andriy Lysenko, a spokesman for Ukraine's national security council.