Kiev on Wednesday said a massive convoy of tanks and heavy weapons from Russia was travelling towards a government-held town in restive east Ukraine.
A convoy of "up to 100" tanks, armoured vehicles and rocket launchers was seen travelling on a road toward Telmanove, a town about 80 kilometres south of rebel stronghold Donetsk and 20 kilometres from the Russian border, Ukraine's army said in a statement.
The army did not give details about the personnel on board the vehicles or when the column is thought to have entered Ukraine.
A military source told AFP that the convoy had come from Russia.
"We believe that this is Russian equipment. You cannot buy 100 tanks at a market in Donetsk or Lugansk," the source said.
"Of course they have been moved from across the border," he added.
It is unclear if this column is the same as an armoured convoy identified by Kiev earlier this week as having crossed from Russia's Rostov region to Ukraine's restive southern Donetsk region.
On Wednesday, AFP journalists travelling on the same road heading south to Telmanove said they traces of tank tracks and heard explosions.
Ukrainian military also said that a smaller group of vehicles had crossed the border from Russia about 110 kilometres east of Donetsk and travelled on to the rebel stronghold.
The convoy included "six Grad rocket launchers, eight covered Kamaz (trucks) and two Ural trucks with manpower," the statement said.