BOGOTA, Colombia — Colombia freed Ingrid Betancourt and three American military contractors from leftist guerrillas yesterday after military spies tricked rebels into giving them up without a single injury, the defense minister said.

In all, the operation freed 15 hostages including Colombian soldiers and police, Juan Manuel Santos said.

The rescue is the most serious blow ever dealt to the 44-year-old Revolutionary Armed Forces of Colombia, who considered Ms. Betancourt and the three Americans their most valuable bargaining chips.

In Paris, the French-Colombian politician’s son Lorenzo Delloye-Betancourt called her release after six years of captivity, “if true, the most beautiful news of my life.” There was no answer at the homes of American families of the three U.S. hostages: Marc Gonsalves, Thomas Howes and Keith Stansell.

Mr. Santos said the military intelligence agents infiltrated the guerrilla ranks and led the local commander in charge of the hostages, alias Cesar, to believe they were going to take them by helicopter to Alfonso Cano, the guerrillas’ supreme leader.

Surrounded by military commandos, Cesar and the other guerrillas gave up without a fight as they helicopters took the hostages to a military base in Guaviare.

Betancourt was abducted in February 2002 as she was running for president. Because she also holds French citizenship, France’s government has campaigned for her release. She turned 46 on Christmas Day.

The Americans were captured a year later when their drug surveillance plane went down. They worked for a Northrup Grumman Corp. subsidiary as Pentagon contractors. They were the longest-held American hostages in the world.

Since their abduction, families of the American hostages have received only two “proof of life” videos, the latest in November.

That latest tape also showed the first images in years of Ms. Betancourt, who hadn’t been seen since 2003. The images, along with letters and reports from other hostages, described a once-vibrant, confident woman slowly succumbing to Hepatitis B, tropical skin diseases, and depression.

One former hostage said Ms. Betancourt was kept chained to a tree after trying to escape.

Ms. Betancourt’s family waged a campaign for her freedom, organizing marches and events in Colombia and France, where her case became a cause celebre. President Sarkozy of France implored the FARC to free the ailing Ms. Betancourt and sent a mission to Colombia to try to gain access to her. He also urged Colombia’s government to contact the rebels.

President Chavez of Venezuela, who shares an affinity with the leftist FARC, also tried to negotiate Ms. Betancourt’s release as part of a prisoner swap.

But none of the efforts could bridge the gaps between the guerrillas and President Uribe of Colombia, whose father was killed by the FARC and who made the group’s defeat the cornerstone of his presidency.