It was the latest in a series of reported arrests of senior Abu Sayyaf men as operations against the group are intensified.
Three of the four were arrested in a coastal village near the port city of Zamboanga on Mindanao island yesterday night, said city police chief Senior Superintendent Angelito Casimiro.
"We recovered from them documents of a plan to kidnap a local businessman and a son of a shipyard owner," Casimiro said.
Earlier on the same day, Casimiro said combined military and police intelligence units arrested Sattar Sabtula, an Abu Sayyaf member involved in the 2002 kidnapping of a group of Jehovah's Witness missionaries on the nearby island of Jolo, a rebel stronghold.
Two of the missionaries were beheaded while four others were freed after months in captivity following ransom payments, police said.
On June 11 Khair Mundos, listed as one of the "most wanted" terrorists by the US government which put a USD 500,000 reward on his head, was captured in a Manila suburb.
The Abu Sayyaf is a small gang of Islamic militants blamed for the country's worst terrorist attacks, including a 2004 ferry bombing that left over 100 dead.
Founded in the 1990s with seed money from Al Qaeda, the group has survived over the past decade by drawing support from poor Muslim communities that have become fertile recruiting ground.
The US military has had about 500 troops rotating through the southern Philippines since 2002 to train Filipino soldiers to combat the insurgents.
