Fernando Baldomero, who escaped an attempt on his life earlier this year, was gunned down in front of his house as he was about to take his child to school, according to local human rights group Karapatan.
He died on the way to the hospital from wounds to his head and neck, said provincial police chief Epifanio Bragais.
The Philippines has been wracked by extrajudicial killings in the last two decades, which local human rights groups have largely blamed on security forces. The military often describes the victims as communist rebels, who have been fighting for a Marxist state.
But Karapatan said more than 1,000 of those killed have been left-wing activists, party members and farmers. In most cases, the assailants have escaped and the cases remain unsolved, the group said, calling for an immediate investigation into the latest attack.
Baldomero was the chairman of Bayan Muna political party and a member of his village council in the province of Aklan. Police quoted witnesses as saying the gunmen sped away on a motorcycle without license plates.
Aquino, who succeeded Gloria Macapagal Arroyo, has promised to jail perpetrators and seek justice for the victims of such killings.
Amnesty International on Monday urged new Justice Secretary Leila de Lima, the former head of the independent Commission on Human Rights, to end impunity for the rampant killings and enforced disappearances and to improve protection for witnesses.
“In the Philippines, members of the military, police, state-supported militias and ‘private armies’, as well as insurgent groups, have literally been allowed to get away with murder,” said Sam Zarifi, Asia-Pacific director of the human rights watchdog.
