Philippines police have arrested more than 60 people and found a major arms and ammunition cache, in raids after a poll-related massacre in the south.
The crackdown, on a clan linked to the massacre, came after President Gloria Arroyo declared martial law in Maguindanao province.
It is the first time martial law has been used in the country since the fall of autocrat Ferdinand Marcos in 1986.
Fifty-seven people including 30 journalists died in the massacre.
Officials said they acted after receiving reports that armed groups loyal to the Ampatuan clan were planning an insurrection.
The clan has long controlled Maguindanao and its members have been loyal supporters of President Arroyo.
Correspondents say businesses were closed and streets empty in the mainly Muslim province, as troops backed by tanks and aircraft took control.
Police arrested 15 people at a ranch owned by the family, bringing the total number detained to 62.
Former Maguindanao governor Andal Ampatuan Sr, and four of his sons, were among suspects held earlier in the week. They deny involvement in the 23 November massacre.
One of the sons, Andal Ampatuan Jr, is suspected of orchestrating the killings and has been charged with 25 counts of murder.
The latest of several weapons caches was found on Sunday at a farm thought to be owned by the Ampatuans near the provincial capital Shariff Aguak, military officials said.
About 40 firearms and hundreds of crates of ammunition were discovered.
The BBC's Rachel Harvey says the declaration of martial law is a politically sensitive move by President Arroyo.
The government said it had intelligence that armed groups were plotting an offensive.
Since the killings, Mr Ampatuan Sr and other members of the family have been expelled from her party.
The government has armed militias in the south to act as an auxiliary force to the army and police battling insurgents but they often end up as the private armies of local strongmen.
Former Philippine leader Ferdinand Marcos imposed martial law nationwide from 1972 until 1981. He stayed in power until 1986.
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