"A Ukrainian defense spokesman says a group of Russian tanks and military vehicles have crossed into the far southeastern corner of the country, potentially opening up a new front in the government's ongoing conflict with pro-Russian separatists.

"It is the latest charge from Ukraine that Russia has been helping separatists fighting against government troops in the eastern part of the country.

"Russia's foreign minister denied having any knowledge of the incident Monday. But he announced that Russia would send a second aid convoy to eastern Ukraine sometime this week.

"Last Friday, Russia sent a shipment of humanitarian goods into eastern Ukraine without the government's permission."