Ukrainian forces guard a checkpoint today in the eastern part of the country. Ukraine President Petro Poroshenko called for an emergency meeting of his nation's security council after declaring that Russian troops had crossed the border.

NOVOAZOVSK, Ukraine — “Russian forces have entered Ukraine,” the country’s president declared today, cancelling a foreign trip and calling an emergency meeting of his security council. Reports from analysts to separatist rebels to NATO and U.S. officials backed up that assessment.

President Petro Poroshenko summoned the council as the strategic southeastern town of Novoazovsk appeared firmly under the control of separatists and their Russian backers, a new front in the war in eastern Ukraine between the separatists and Poroshenko’s government in Kiev.

“Today the president’s place is in Kiev,” Poroshenko said.

Russian stock markets dived as fears grew that the country was escalating its role in the conflict, a move that could provoke the U.S. and European Union to impose further sanctions on Russian businesses and individuals. Russia’s MICEX index dropped nearly 2 percent today, and major Russian state banks VTB and Sberbank dropped more than 4 percent.

The leader of the insurgency, Alexander Zakharchenko, said in an interview on Russian state television that 3,000 to 4,000 Russians have fought on the separatist side since the conflict began in April.

A NATO military officer in Brussels told The Associated Press that “we assess there are over 1,000 Russian troops operating inside Ukraine” now. He said NATO estimates that another 20,000 Russian troops are close by, right over the Russian border. He spoke Thursday on condition of anonymity.

The U.S. government accused Russia of orchestrating a new military campaign in Ukraine, helping rebel forces expand their fight and sending in tanks, rocket launchers and armored vehicles.

“These incursions indicate a Russian-directed counteroffensive is likely underway in Donetsk and Luhansk,” U.S. State Department spokesman Jen Psaki said. She voiced concern about deliveries of materiel in southeast Ukraine near Novoazovsk and said Russia was being dishonest about its actions, even to its own people.

Russian forces, she said, are being sent 30 miles inside Ukraine, without them or their families knowing where they are going. She cited reports of burials in Russia for those who have died in Ukraine and wounded Russian soldiers being treated in a St. Petersburg hospital.

This morning, an Associated Press journalist saw rebel checkpoints near Novoazovsk and was told he could not enter. One of the rebels said there was no fighting in the town.