May 27, 2001 Abu Sayyaf kidnaps three U.S. citizens and 17 Filipinos from a resort off the coast of the southern Philippine island of Palawan and demands ransoms. The Americans are Guillermo Sobero, of Corona, Calif., and Martin and Gracia Burnham, missionaries from Wichita, Kan.
June 12, 2001 Abu Sayyaf spokesman Abu Sabaya claims the group beheaded Guillermo Sobero, an American it was holding hostage, as an "independence day gift" for President Gloria Macapagal Arroyo of the Philippines.
July 8, 2001 Philippine authorities arrest Nadzmie Sabtulah, also known as Commander Global, saying he is a high-ranking Abu Sayyaf leader and his capture is "a great setback" for Abu Sayyaf.
Sept. 24, 2001 President Bush includes Abu Sayyaf among groups targeted in an executive order to freeze financial assets of suspected terrorists.
Oct. 1, 2001 Former President Joseph Estrada goes on trial on plundering charges, which constitute a series of criminal acts resulting in at least $1 million of illegally acquired wealth. The charge carries a maximum penalty of death, and the trial could take a year or more.
Oct. 5, 2001 The U.S. government withdraws officials from the southern Mindanao region of the Philippines, as the State Department cites Abu Sayyaf in a travel advisory warning Americans not to visit the region.
Oct. 12, 2001 U.S. Embassy officials in Manila confirm headless skeletal remains found Oct. 8 in a Basilan island jungle were those of Guillermo Sobero, an American kidnapped by Abu Sayyaf in May.
Nov. 20, 2001 U.S. President George Bush tells visiting Philippines President Gloria Macapagal Arroyo that the U.S. will help fight Abu Sayyaf. He agrees to ask Congress for millions of dollars for the effort, and vows to reporters the U.S. will act "in any way [Arroyo] suggests in getting rid of Abu Sayyaf."
Nov. 24, 2001 MNLF leader Nur Misuari, wanted in the Philippines after allegedly renewing his fight for Islamic independence in the southern part of the country, is arrested in Sabah, Malaysia, for entering that country without official documents.
Nov. 26, 2001 A Philippines cable television station broadcasts an interview with Martin and Gracia Burnham, a Wichita, Kan., couple held by Abu Sayyaf. The interview, which the station says was made the prior day, marks the first glimpse of the couple on videotape since their abduction on May 27.