Clashes in Slovyansk have led to the deaths of five paramilitary police according to Kyiv. Thirty military personnel were injured.

Government troops took control of a TV tower while rebels retreated deeper into the city, according to the Russian Interfax agency.

“An anti-terrorist operation led to an ambush of terrorists. They are using heavy machine guns and heavy weapons to engage in fighting with us,” said Arsen Avakov, Ukrainian Interior Minister.

The crew of a Ukrainian military helicopter survived after it was shot down and crashed into a river the interior ministry said in a statement.

Separatists said four of their fighters were killed while local media sources say 15 were injured.

A barrier was erected near a local hospital were the injured rebels were treated. Some of the victims, it’s reported came from the local population.

It’s estimated around 800 pro-Russian militants were involved in the clashes.

Moscow warned Kyiv on Monday a humanitarian crisis was looming in blockaded towns in the east and called on the government to stop using force against its people.

It said Kyiv should, “withdraw forces and sit down at the negotiating table to begin a normal dialogue about ways to resolve the political crisis.”

Witnesses said the fighting was among the heaviest they have seen so far in the rebel stronghold.