At least 20 people have been killed after a suicide bomber blew himself up inside a Sunni mosque during a sermon in central Iraq.

The explosion took place in the town of Wajihiya in the ethnically and religiously diverse province of Diyala.

The area has seen an increasing number of attacks in recent weeks, but it was unclear who was behind this latest blast.

The recent attacks have raised fears of a return to full-blown sectarian conflict in a country where Kurds, Shia and Sunni Muslims have yet to find a stable way of sharing power.

Separately, a suicide bomber tried to enter a Shia mosque in Jbeila, north of Hilla, 100km south of Baghdad.

He failed and blew himself up, killing a policeman who had blocked his way.

Another policeman was killed in an almost identical incident last night in the town of Iskandariya, also north of Hilla, police said.

Sectarian tensions have been inflamed by the civil war in neighbouring Syria.

The Syrian conflict has drawn in Shia and Sunni fighters from Iraq and beyond to fight on opposite sides of the conflict.

Sunni Islamist insurgents, including the al-Qaeda-affiliated Islamic State of Iraq, have been regaining strength in recent months, security sources say.