Ukrainian President Petro Poroshenko on Monday accused Russia of this week sending three military convoys over the border into the separatist-controlled east.

"Just this week three big convoys crossed our border towards Lugansk, Donetsk and Debaltseve," he said, referring to rebel-controlled areas of eastern Ukraine.

Poroshenko accused Russia of having sent a total of up to 500 tanks, 400 artillery systems and up to 950 military armoured vehicles to pro-Russian rebels, although he did not specify the time period for these deliveries.

He was speaking at a military parade in Kiev to celebrate 24 years since Ukraine gained independence from the Soviet Union.

"The war for independence is still continuing and we can only claim victory by combining our defensive efforts, diplomatic talent, political responsibility and steely endurance," Poroshenko said.

A peace deal reached in Minsk in February has repeatedly been broken by both sides. The death toll in the 16-month-long war is now close to 6,900.