The Ukrainian army has begun a special operation against pro-autonomy activists in the eastern town of Slavyansk. The city is now blockaded by the Ukrainian military

The Ukrainian army has begun a special operation against pro-autonomy activists in the eastern town of Slavyansk. The city is now blockaded by the Ukrainian military, with 20 helicopters reportedly deployed to crack down on self-defense forces.

Two helicopters have been shot down by self-defense forces, according to reports. Earlier, two helicopters were allegedly downed, with two pilots dead and another one captured, RIA Novosti news agency reported. This information was confirmed by Ukraine's coup-appointed Interior Minister Arsen Avakov.

The total death toll in Slavyansk currently stands at three: besides the two troops, there is also one fatality among the defense forces. Both sides report injuries.

Also, a journalist’s car has reportedly been fired on, according to RT's Paula Slier who is trying to reach the scene, but the Ukrainian army seems to be blocking all entrances to the city - and even Kramatorsk.

The Slavyansk self-defense leader said that helicopters were firing on the city with missiles, but that there have been no reports of damage, Interfax stated.

Slavyansk self-defense forces told RIA Novosti that the Ukrainian military had attacked several positions.

“The attack is targeting a few checkpoints at the same time. A few armored vehicles and airborne combat vehicles arrived and airborne troops descended from the helicopters and attacked the checkpoints. Some forces were dropped off around the train station, where we didn’t have anyone,” RIA Novosti quoted the press secretary of the Slavyansk self-defense units as saying.

Early on Friday morning, a city siren – which is designed to warn local residents of a Ukrainian military attack – went off and shots were heard. A few minutes later, the siren stopped and everything calmed down, according to reports.

A few of the activists were injured during the attack, Interfax cited the city’s self-defense unit as saying.

A commander at one of the checkpoints told RIA Novosti that the Ukrainian army had taken control of one of the roadblocks on the outskirts of Slavyansk, as well as the city’s TV broadcasting center. The Ukrainian army was mounting artillery positions around the captured TV station in Slavyansk, a city administration spokesman said, as cited by RIA Novosti.

A police station was reportedly seized, while the city center remains quiet, RT’s Paula Slier reported from Ukraine. Several armored vehicles have been seen outside Slavyansk, she added.

Thick smoke was spotted on the outskirts of the city, where the roadblocks are located.

Meanwhile, the OSCE is trying to reach the Ukrainian authorities in attempt to stop the military operation in the country’s southeast, after a request from Russia.

“We’ve demanded that all that be stopped, and that humanitarian corridors be created for the civilian population, and all air forces flights halted,” the Russian permanent representative to the organization, Andrey Kelin, told RIA Novosti news agency.

Injuries have been reported as hundreds of people from rival rallies clash in Ukraine's port-city of Odessa. A pro-unity demonstration, which included nationalists and football fans, ran into a rally preaching greater autonomy for the regions.