The UN Security Council has begun meeting in New York in response to claims that Russia has invaded Ukraine. NATO says at least 1,000 Russian troops are stationed in the key city of Novoazovsk.

All updates in Universal Coordinated Time (UTC)

18:05 – United Nations Security Council convenes emergency meeting to discuss ways to help de-escalate situation in eastern Ukraine.

16:25 Germany’s Chancellor warns that Russia could now face tougher sanctions as a result of the escalation of the conflict in eastern Ukraine. Angela Merkel said EU ministers are scheduled to meet on Saturday. “We are getting reports of an increased presence of Russian soldiers and of new unrest and fresh advances of the separatists in areas that until now were very quiet,” she told a news conference on Thursday after talks with Balkan leaders.

16:23 – Spokesman for UN Secretary General Ban Ki-Moon calls reports of firing in Ukraine a “dangerous escalation.” “The international community cannot allow the situation to escalate further nor can a continuation be allowed of the violence and destruction that the conflict has wrought in eastern Ukraine,” UN spokesman Stephane Dujarric told reporters.

16:20 – Russia rejects claims that its military is stationed in Ukraine. Defense spokesman quoted by Interfax as saying allegations of Russian presence in eastern Ukraine bear “no relation to reality.”

15:35 – North Atlantic Treaty Organization says ambassadors of its 28 members and Ukraine will hold an emergency meeting on Friday to discuss the situation. Ukraine is not a NATO member but meets regularly with the organzation in a body called the NATO-Ukraine Commission.

14:57 – NATO Spokeswoman Oana Lungescu, on official NATO Twitter account, publishes satellite imagery displaying ostensible Russian presence inside Ukraine.

14:41 – Ukrainian President Petro Poroshenko tells Interfax that situation is “difficult, yet controllable,” following losses to Russian forces in eastern Ukraine. Poroshenko, who met with top security and defense chiefs after the key town of Novoazovsk fell to Russian-backed separatists, said Russian troops had come “to the rescue” of the rebels after Kyiv’s earlier military successes.

14:32 – Russian state broadcaster, RT, via Berlin-based video news agency Ruptly, publishes footage of separatists in Novoazovsk raising flag atop municipal building.