Manila, Jan 30 (IANS): A grenade attack on a mosque in the Philippine city of Zamboanga City killed two persons early on Wednesday, authorities said.

This comes just days after a deadly Catholic cathedral bombing and a vote backing Muslim self-rule, Channelnews Asia reported.

"A grenade was lobbed inside a mosque killing two persons and wounding another four," regional military spokesman Lieutenant Colonel Gerry Besana said.

Besana said it was too early to say whether the mosque blast was in retaliation to the cathedral attack, adding police were hunting for those responsible.

The victims were sleeping inside the mosque at the time of the attack on the insurgency-plagued island of Mindanao, which is home to the Philippines' Muslim minority.

The blast came even as the island nation was on high alert after the cathedral bombing that killed 21 people at a Sunday mass on the remote Muslim-majority island of Jolo.

The Islamic State group has claimed responsibility for the cathedral blast.

Philippine authorities initially said it was not a suicide attack, but on Tuesday President Rodrigo Duterte contradicted them saying one of the bombers had blown himself up outside the cathedral.