Several others were wounded in the ambush and the gunmen escaped, the airport’s manager, Jose Angel Honrado, said during a news briefing on Friday.
The mayor, Ukol Talumpa of the small southern Philippine town of Labangan, had arrived at the airport about 11 a.m. on a flight from the southern city of Zamboanga and was waiting to be picked up in front of the airport when the men opened fire on the busy loading area in front of the terminal, officials said.
Also killed in the attack were his wife, Lea Talumpa, their 25-year-old nephew, Salipudin Talumpa, and an 18-month-old boy who was the child of a bystander at the airport, officials said.
Leila de Lima, the secretary of the Department of Justice, said Friday that there had been two previous attempts to kill the mayor, who was elected to the office in May. The province where the mayor holds office, Zamboanga del Sur, is in an area where political violence is common.
Ms. de Lima said that the country’s National Bureau of Investigation was looking into the case but that it was not clear whether the killing was related to politics or other issues.
“We are still investigating the motive,” said Mr. Honrado, the airport manager.
Mr. Talumpa was shot in the chest. His wife and the 18-month-old child were shot in the head, Mr. Honrado said. The nephew was shot multiple times in the head and chest, he said.
The area where the shooting occurred is a publicly accessible passenger loading zone outside the terminal building, Mr. Honrado said. He said that there was no closed-circuit television camera coverage in the area of the incident.
A spokesman for President Benigno S. Aquino III said Friday that security would be enhanced at the airport and that the president was monitoring the investigation.
“We condemn this blatant act of violence that has killed an innocent bystander and imperiled the safety of citizens in the airport,” said Herminio Coloma Jr., the spokesman. “The Philippine National Police is conducting hot pursuit operations against the suspected assailants.”