Almost 100 people, mostly women and children, died as a ferry packed with families celebrating Kurdish New Year sank in a swollen river in the former jihadist stronghold of Mosul, in Iraq's worst accident in years.

Most of the victims were women and children, the interior ministry said. It is thought nearly 200 people were on board. The vessel was crammed with men, women and children crossing the Tigris Thursday to go to a popular picnic area to celebrate Nowruz, the Kurdish New Year and a holiday across Iraq marking the start of spring. Mosul's civil defence agency reportedly said most on board could not swim.

Prime Minister Adel Abdel Mahdi decreed three days of national mourning as he visited the site of the tragedy. He ordered a swift investigation "to determine responsibilities".

A Mosul security source said the high water levels and overcrowding on the boat, with well over 100 people on board, had been to blame for the disaster."The boat sank because there were too many passengers on board.Iraq's justice ministry said it had ordered the arrest of nine ferry company officials and banned the owners of the vessel and the tourist site from leaving the country.

The authorities had warned people to be cautious after several days of heavy rains led to water being released through the Mosul dam, causing the river level to rise.

According to sources search operations stretched far downstream from the site where the boat sank. Ambulances and police vehicles transported the dead and wounded to hospitals in the city of nearly two million people.