More than 70 people are reported to have died after a ferry sank in the Tigris river in Iraq’s city of Mosul.

Most of the passengers on board could not swim, the head of Mosul’s civil defence agency said. Reports suggest nearly 200 people were on board.

The ferry was said to be heading towards a tourist island as part of new year celebrations.

Prime Minister Adel Abdul Mahdi has ordered an investigation “to determine responsibilities”.

In a statement Mr Mahdi said he was following the story “with pain and sadness”, and had ordered “all state efforts” to find survivors and treat victims.

Health and security sources said 72 people were killed, with 67 rescued and 55 still missing.

Jeanine Hennis-Plasschaert, the special representative for Iraq of the United Nations secretary general, said it was a “terrible tragedy”.

“Our hearts go out to the families and relatives of the victims,” she said in a statement.

Authorities had reportedly warned people about rising water levels as the gates of the Mosul dam had been opened, and some are accusing the ship operator of ignoring the advice.

Images on social media showed the upturned vessel and people floating in the fast-flowing river.

Ambulances and helicopters arrived to find survivors and bodies of those killed.