HO CHI MINH CITY, Vietnam — The Philippines captured a top leader of a militant group on Wednesday who the United States says funneled money from Al Qaeda to Filipino rebels blamed for more than a decade of bombings, beheadings and kidnappings in the southern part of the country.

Khair Mundos, 50, a leader of Abu Sayyaf, was arrested on Wednesday morning at his in-laws’ house in a densely populated section of southern Manila, according to a statement from the police. The police had the house under surveillance for two months before the arrest.

The United States has been helping in the fight against Abu Sayyaf for years, with a contingent of about 500 United States special forces troops stationed in the southern Philippines after the Sept. 11, 2001, attacks.

In the past decade, the number of Abu Sayyaf fighters has dwindled to fewer than 400, and the group has focused on kidnapping-for-ransom operations in pursuit of profit rather than ideology, according to Pacific Strategies and Assessments, a risk assessment group based in Manila.