MANILA, Philippines -- Gunmen killed a Philippine town mayor and wounded his vice mayor and at least three other companions in an ambush on Monday while they were travelling in a van in a far-flung southern region, officials said.

Such violence has long tarnished Philippine politics, especially in remote rural regions burdened with weak law enforcement, illegal firearms, political and clan conflicts and decades-long insurgencies.

Mayor Randy Climaco and his companions had come from a village fiesta and were returning home in a van when they came under attack Monday afternoon in his town of Tungawan in Zamboanga Sibugay province. The heavily-armed attackers escaped, police said.

Gov. Wilter Palma said Tungawan Vice Mayor Abduraup Abison was in serious condition in a hospital after being shot in the head.

Climaco's term as mayor was due to end next year and a cousin who was planning to run in next year's elections to succeed him was travelling with him but was not hurt in the attack, Palma said.

Investigators were trying to determine the identity of the gunmen and the motive of the attack. Muslim rebels and other outlaws have a presence in Zamboanga Sibugay, about 800 kilometres (500 miles) south of Manila, but it was not immediately clear if they had a role in Monday's attack.