NOVOAZOVSK, Ukraine -- Their tanks bearing the flag of their would-be state, Russian-backed separatists held control Friday over this coastal town on the new front in the Ukraine conflict and announced their intention to keep pushing west toward a major port city.
None of the half-dozen tanks seen by Associated Press reporters in the town of about 12,000 people bore Russian markings, but the packaging on their field rations said they were issued by the Russian army.
The Ukrainian government the day before accused Russia of sending tanks, artillery and troops across the border, and NATO estimated at least 1,000 Russian troops were in Ukraine.
As tensions rose, European Union foreign ministers called for heavier sanctions against Moscow ahead of Saturday's summit of EU leaders in Brussels. Ukrainian President Petro Poroshenko was invited to address the summit.
The rebels denied they are getting Russian military vehicles.
"We are fighting with the machinery the (Ukrainian forces) abandon. They just dump it and flee," said a rebel commander.
Although such claims of using only confiscated Ukrainian equipment are common, top rebel leader Alexander Zakharchenko himself has said Russia was supplying equipment and fighters -- something Moscow has steadfastly denied doing.
"Despite Moscow's hollow denials, it is now clear that Russian troops and equipment have illegally crossed the border," NATO Secretary-General Anders Fogh Rasmussen said Friday. "This is a blatant violation of Ukraine's sovereignty and territorial integrity. It defies all diplomatic efforts for a peaceful solution."
A spokesman for the rebels in Novoazovsk, who identified himself only as Alexander, said their plan was to push westward to the major port city of Mariupol, about 35 kilometers (20 miles) away.
There was no sign of imminent movement on Friday, but Alexander's statement underlined fears that the rebels' eventual aim is to establish a land bridge between the Russian mainland and the Crimean Peninsula, which was annexed by Russia earlier this year.
Speaking at a Kremlin-organized youth camp on Friday, Russian President Vladimir Putin likened the Ukrainian government's efforts to put down the separatist uprising to the Nazi siege of Leningrad in 1941-44.
The Leningrad comparison is a powerful one for Russians and clearly aimed at portraying the Ukraine conflict in stark, good-versus-evil terms. The 872-day siege, in which at least 670,000 civilians died, is seen by many Russians as one of the most heroic chapters in the country's history.
To stop the bloodshed, the Kiev government should open talks with the rebels, Putin said.
The death toll in the fighting reached nearly 2,600 as of Wednesday, said Ivan Simonovic, U.N. assistant secretary-general for human rights. He described the humanitarian situation in eastern Ukraine as "alarming," with people unable to leave cities caught up in the fighting.
The U.N. human rights office on Friday accused both sides of deliberately targeting civilians.
The separatists have carried out murders, torture and abductions along with other serious human rights abuses, while Ukraine's military is guilty of such acts as arbitrary detentions, disappearances and torture, the organization said in a report.
At a meeting in Milan, several EU foreign ministers accused Russia of invading eastern Ukraine and said Moscow should be punished with additional sanctions. The diplomats were expected to draw up measures that could put before the EU heads of state on Saturday.
The head of the EU's executive Commission, Jose Manuel Barroso, warned Putin that further destabilization of Ukraine "will carry high costs."
Putin called on the separatists to release Ukrainian soldiers who have been surrounded by the rebels in eastern Ukraine. He appeared to be referring to soldiers trapped outside the town of Ilovaysk, east of Donetsk, for nearly a week.
Zakharchenko, the rebel leader, said the Ukrainian troops would have to lay down their arms before they would be allowed to go "so that this weaponry and ammunition will not be used against us in future."
A spokesman for Ukraine's national security council, Col. Andriy Lysenko, rejected the demand: "Ukraine is not ready to surrender arms and kneel in front of the aggressor."
Ukraine, meanwhile, got a boost from the International Monetary Fund, which said Friday it had approved payment of a $1.39 billion aid installment as part of a financial support package. The sum brings the total that has been paid out to $4.51 billion, out of $16.67 billion due over two years.
For the second day, Russian markets reacted nervously to the escalation of the conflict, with the Russian ruble sliding to the all-time low of 37.10 rubles against the dollar in early morning trading. It recovered later to 36.90 rubles.
Juergen Baetz reported from Milan. Nataliya Vasilyeva in Moscow, Jim Heintz in Kiev, and Raf Casert in Brussels contributed reporting.