A search operation was under way on Sunday for a border guard official missing after a patrol boat sank off Ukraine"s port city of Mariupol following an explosion, the border guard said.

One crew member died and five others were being treated for injuries, local police were quoted as saying by Interfax news agency.

The cause of the explosion was not immediately clear, authorities said.

Reportedly, the ship was hit by a landmine. The situation is grave in the anti-terrorist operation zone. In the east of Ukraine eight Ukrainian soldiers were wounded as a result of violation of ceasefire regime.

It was reported that the head of contact group of the OSCE resigns. The reasons of Heidi Tagliavini`s resignation hav not been named.

In an interview to the Italian newspaper "Corriere della Sera", the Russian president responded to the current situation. Vladimir Putin said that Russia would do everything so that Minsk agreement is executed by all parties.