A man hurled a grenade into a mosque in the southern Philippines during weekly prayers on this morning, killing three people and wounding many more, police said.
The attack took place in the town of Midsayap in the southern region of Mindanao.
"We are still conducting an investigation. We still do not know the motive or the identity of the perpetrator. I believe it was done by only one person because a witness said so," the town's police chief Mr Eduardo Marquez said.
A military spokesman confirmed there had been an explosion, while another witness said two grenades were thrown into the small but crowded mosque.
Local radio reported that as many as three people had been killed while up to 16 people had been wounded. Mr Marquez said most of the people inside the mosque were employees of the government's National Irrigation Administration.
The southern region of Mindanao is considered the homeland of minority Muslims in the mainly Catholic Philippines.
Four Muslim militant groups, including the Moro Islamic Liberation Front and the Abu Sayyaf, have been fighting for an Islamic state in Mindanao.