A suicide bomber made his way into a Shiite mosque north of Baghdad and blew himself up in the middle of a packed funeral on Wednesday, killing 42 people and leaving corpses scattered across the floor.

The attack is likely to heighten tensions as Iraq grapples with a political crisis and more than a month of protests in Sunni-majority areas that have hardened opposition to Shiite Prime Minister Nuri al-Maliki.

No group claimed responsibility, but Sunni militants often launch attacks in a bid to destabilise the government and push Iraq back towards the sectarian violence that blighted it from 2005 to 2008.

The bomber struck at the Sayid al-Shuhada mosque in Tuz Khurmatu, 175 kilometres north of Baghdad, and targeted the funeral of a relative of a politician who was shot dead a day earlier.

“Corpses are on the ground of the Husseiniyah (Shiite mosque),” said Shallal Abdul, mayor of Tuz Khurmatu. “The suicide bomber managed to enter and blow himself up in the middle of the mourners.”

Niyazi Moamer Oghlu, secretary general of the provincial council of Salaheddin, put the toll at 42 dead and 75 wounded.