Philippine authorities have charged a town mayor with mass murder in connection with an election-related massacre of 57 people that shocked the nation.

Andal Ampatuan Jr. was charged Friday after authorities flew him to the capital, Manila, from the southern Philippines, where he turned himself in the day before.

Ampatuan is the mayor of Datu Unsay, a town in Maguindanao province, where he is suspected of orchestrating Monday's attack on a convoy of journalists, supporters and relatives of a rival politician.

The convoy was traveling to register politician Ismael Mangudadatu as a candidate for provincial governor when about 100 gunmen ambushed it and slaughtered the occupants. The dead included Mangudadatu's wife, sisters and 29 journalists.

Authorities suspect Ampatuan of ordering the massacre to stop Mangudadatu from running for governor, a post held by Ampatuan's father, Andal Ampatuan Sr.  Mangudadatu filed his candidacy Friday, saying only death could keep him from contesting next year's election.

The Ampatuan clan has ruled Maguindanao unopposed for years.  Maguindanao governor Andal Ampatuan Sr. had been grooming the younger Ampatuan to succeed him.

Media groups say Monday's massacre was the deadliest single attack on journalists ever recorded anywhere.

The younger Ampatuan says he is innocent and has blamed the killings on the Moro Islamic Liberation Front.  The Muslim separatist group says it had nothing to do with the killings.  Authorities also say there is no evidence of rebel involvement.

The massacre's brutality has shocked Philippine society and increased pressure on the government to crack down on families who run parts of the country as private fiefdoms.

Some information for this report was provided by AFP.