Amid the escalating violence in eastern Ukraine, Russia has called for an emergency U.N. Security Council meeting on the crisis, which is pitting pro-Russia militias against the Ukrainian army and civilians who support a united Ukraine.

A spokesman for Russia’s permanent mission at the United Nations told Russian government-owned ITAR-TASS News Agency on Friday that Ukrainian special forces have started what he called a “punitive operation” in the city of Slovyansk in eastern Ukraine.

Pro-Russian forces there shot down two Ukrainian military helicopters on Friday with what were thought to be shoulder-fired anti-aircraft missiles, Ukraine’s defense ministry told Interfax news agency. At least one pilot was killed, in an act of unprecedented violence that has many observers concerned that Ukraine may be on the brink of a civil war.

The Ukrainian government also said that “many” rebels had died and were wounded during the first major offensive against pro-Russian militias. According to the Associated Press, two Ukrainian soldiers had died and seven were wounded in Friday's clashes in Slovyansk.

Meanwhile, the Ukraine crisis will be the focus of a meeting between U.S. President Barack Obama and German Chancellor Angela Merkel on Friday in Washington. The two will speak to the public in a press conference at 11:40 a.m. Washington time. Germany is Russia's biggest trading partner in Europe, and the two are expected to discuss the effect of U.S. sanctions on Russia. The European Union has imposed sanctions of its own, although not as harsh as those imposed by Washington.

On the ground, clashes have extended Friday to the city of Odessa, located in the south part of Ukraine, between pro-Ukrainian crowds and pro-Russian rioters. Pro-Russian militants attacked a rally of 1,500 people who were demonstrating for national unity. According to various media reports, several people have been injured and Russian media is reporting that between one and three people have died so far.

The situation on the ground in Odessa is still confusing; people reporting from the ground through social media are unclear on who is fighting for which side. Live streams of the clashes show people setting up barricades with furniture and garbage dumpsters in the streets, while others mix what look like molotov cocktails. Riot police seem to have almost no effect on the fighting on the ground. Forces appeared sporadically throughout the fighting on the streets but were immediately surrounded and forced to retreat.