SHARIFF AGUAK, Philippines — Officials say Philippine police have clashed with gunmen loyal to a powerful clan accused in the country's worst political massacre.

National police chief Jesus Verzosa says there were no causualties Sunday in the first reported violence since the government put southern Maguindanao province under martial law.

He says about 20-30 suspected followers of the Ampatuan clan opened fire on police in Datu Unsay township, near the site of the Nov. 23 killing of 57 people traveling in an election convoy.

Verzosa says more than 2,400 gunmen have massed up in 16 of Maguindanao's 22 townships to defend the Ampatuan clan, which has ruled the province unopposed for years.

Interior Secretary Ronaldo Puno says officials are trying to persuade them to disarm.