Hungary's Foreign Ministry denied Friday a Russian claim that it was supplying Ukraine with weapons, which came after a pro-Moscow Hungarian website said that T-72 tanks had been delivered to Kiev.

German Chancellor Angela Merkel urged Russian President Vladimir Putin to "stop the flow of military equipment, military advisers and armed personnel crossing the border with Ukraine," in a telephone call on Friday. 

The head of the self-proclaimed Donetsk People's Republic, Alexander Zakharchenko, said Friday that the inhabitants desperately need Russian humanitarian aid and accused Ukraine of deliberately stalling its arrival.

"At the moment, the Donetsk people's republic has a very bad humanitarian situation and the help that Russia is sending us and we have still not received, we just need it like air," Zakharchenko said at a briefing in Donetsk.

Two men lift the tarp of a Russian truck near the border with conflict-ridden Ukraine, showing the cargo to around 25 journalists with cameras and microphones in hand.

"What a lot of journalists for sacks of sugar," mutters the driver, Alexander, whose truck is one of 280 that Moscow says are loaded with humanitarian aid.

Ukraine said on Friday it had destroyed part of a Russian military convoy that crossed onto its territory in an incursion that has sent cross-border tensions rocketing.

NATO accused Russia of active involvement in the "destabilization" of eastern Ukraine, where pro-Kremlin separatists have been fighting against Kiev for four months.

Britain has summoned Moscow's ambassador to London over reports of a Russian military incursion across its border with Ukraine, the Foreign Office said Friday.

Alexander Yakovenko was summoned "to clarify reports of Russian military incursion into Ukraine and continued buildup of equipment on border," the ministry said in a tweet.

NATO chief Anders Fogh Rasmussen confirmed Friday an incursion by Russian armored vehicles into Ukraine, saying it showed Moscow's continued efforts to "destabilize" its western neighbor.

"I can confirm that last night we saw a Russian incursion, crossing of the Ukrainian border," he told journalists in Copenhagen after meeting with the Danish defense minister.

Shelling killed 11 civilians and wounded eight more over the past 24 hours in the besieged rebel stronghold of Donetsk in eastern Ukraine, local authorities said Friday.

Fighting raged overnight in central and western districts of the insurgent-controlled industrial hub, the city council said in a statement.

Ukrainian officials were preparing to inspect a massive Russian "aid" convoy bound for the conflict-torn east on Friday after Russian armored vehicles crossed the border, fueling fears Moscow is trying to bolster the unraveling insurgency.

The Ukrainian military had announced that checks had begun on the near 300-truck convoy but later said only that 59 border and customs officials had arrived at a Russian border post to prepare to carry out the inspections.

An alleged Russian intelligence colonel with an obsession for reenacting historical battles, Igor Strelkov, who quit as a key rebel chief on Thursday, was a driving force behind the brutal pro-Moscow insurgency tearing apart east Ukraine.

The Russian citizen -- whose real name is Igor Girkin -- is a fierce nationalist and Orthodox Christian believer who reportedly honed his skills fighting in conflicts from Bosnia to Moldova's breakaway territory of Transdniestr and Chechnya, before helping Moscow seize Ukraine's Crimea peninsula in March.