NATO warns Russia over 'blatant violations' in Ukraine conflict

 NATO warned Russia on Friday over what it described as a "blatant violation" of Ukraine's sovereignty after the West accused Moscow of direct involvement in the escalating conflict, AFP reports.

Fears of a wider confrontation have spiralled after NATO said Russia had sent troops to fight in Ukraine and funnelled huge amounts of heavy weaponry to pro-Kremlin rebels in what Kiev branded an invasion.

"This is not an isolated action, but part of a dangerous pattern over many months to destabilise Ukraine as a sovereign nation," NATO chief Anders Fogh Rasmussen said, describing the massing of Russian troops on the border as a "blatant violation" of Ukrainian sovereignty.

"We urge Russia to cease its illegal military actions, stop its support to armed separatists, and take immediate and verifiable steps towards de-escalation of this grave crisis."

Kiev and the West say Russian troops are spearheading a lightning counter-offensive that has seen rebels seize swathes of southeastern territory from government forces, dramatically turning the tide in the four-month conflict.

Russian President Vladimir Putin has repeatedly denied Moscow is fuelling the conflict or having any troops on the ground in the former Soviet state.

And on Friday, he demanded the Ukrainian government hold "substantial" talks with the separatists who took up arms against Kiev in April, emboldened by Russia's annexation of Crimea the month before.

"I believe that what is happening in Ukraine right now is in principle our common colossal tragedy and it is necessary to do everything for it to stop as soon as possible," he said.

  20,000 troops massed 

NATO said on Thursday Russia had sent at least 1,000 troops to fight alongside the rebels, along with air defence systems, artillery, tanks and armoured vehicles, and had massed 20,000 troops near the border.

And in a move certain to anger Kiev's former masters in Moscow, Rasmussen said NATO was willing to entertain Ukrainian membership after the government said it was taking steps to join.

The new rebel advance has raised fears that the Kremlin could be seeking to create a land corridor between Russia and Crimea on the Black Black Sea.

Mariupol, a strategic government-held port on the Azov Sea south of the main insurgent bastion of Donetsk, was bracing for a possible onslaught after rebels seized several villages nearby.

Residents could be seen driving north with buses crammed full of people displaying signs with "children" written on them, in the hope they would not be fired on.

Some of those standing their ground were digging trenches or bringing in food and other supplies to makeshift barricades were Ukrainian forces were stationed.

The surge in fighting -- which the United Nations says has now killed almost 2,600 people -- came just days after Putin held talks with Ukraine's President Petro Poroshenko but failed to make any significant breakthrough.

"Russia has deliberately and repeatedly violated the sovereignty and territorial integrity of Ukraine, and the new images of Russian forces inside Ukraine make that plain for the world to see," US President Barack Obama said.

"This ongoing Russian incursion into Ukraine will only bring more costs and consequences for Russia."

  'Defenders of New Russia' 

Germany warned the crisis was spiralling "out of control", as EU foreign ministers met ahead of a weekend summit where leaders may draw up further punitive measures on Moscow.

The United States and the European Union have already imposed a series of punishing sanctions on Moscow over the worst standoff between Russia and the West since the Cold War.

But Putin dismissed the concerns and defiantly described the insurgents as defenders of New Russia, a Tsarist-era term for Moscow's former imperial holdings in the region that the strongman has revived since annexing Crimea.

He praised rebel successes in halting Kiev's advances in the counter-offensive in the southeast that has left government troops battling for survival in the town of Ilovaysk and called on rebels to open a "humanitarian corridor".

Putin also insisted that the Russian soldiers captured by Ukrainian authorities ended up in the ex-Soviet country by mistake.

Top rebel leader Alexander Zakharchenko -- who has said Russian troops were in Ukraine "on holiday" -- said his men would be willing to let government troops withdraw if they give up their weapons.

Ukrainian security chiefs lashed out at the Russian proposal, saying it proved rebels were "controlled directly from the Kremlin".

UN chief Ban Ki-moon said the international community had to redouble its efforts to resolve the crisis, and that it was vital elections in Ukraine go ahead as planned in October.

"Lives are at stake. Peace in Ukraine means peace in the region and beyond," he said.

  Surrender or be shot 

Kiev said Thursday that Russian soldiers had seized control of the key border town of Novoazovsk and a string of villages east of Mariupol.

AFP journalists on Thursday saw smoke rising from fighting around Ilovaysk as fighters demanded government troops surrender or die.

Ukraine loyalists have been engaged in a desperate battle for survival in the transport hub for over a week.

"Anyone who surrenders and waves the white flag, will not be shot," a rebel fighter called "Klasik" said.

by Alix RIJCKAERT with Richard LEIN in Moscow and Nicolas GAUDICHET in Mariupol