A lawyer says one of the main suspects on trial for the 2009 massacre of 58 people in the southern Philippines has died of a heart attack.

Salvador Panelo says his client Andal Ampatuan Sr., a former governor of Maguindanao province, died overnight in a government hospital. Ampatuan was brought to the National Kidney and Transplant Institute in early June and was diagnosed with liver cancer.

Ampatuan was among 103 people, including several of his sons and other relatives, who were charged with multiple murder in the Maguindanao massacre, one of the worst political killings in the Philippines.

They were accused of killing 58 people in a convoy of vehicles, which included their political rival and 32 journalists. It was also the world's worst single killing of media workers.