Three Chinese oil workers and their interpreter were freed in Colombia after being held captive for 17 months, a crime authorities blame on FARC rebels though the guerrillas - currently in peace talks with the government - have not claimed responsibility.

A group of unidentified individuals on Wednesday night handed over engineers Zhau Hong, Yang Jing and Tang Guo Fu, as well as their Chinese interpreter, to the International Committee of the Red Cross in a rural area outside San Vicente del Caguan, a town in the southern province of Caqueta.

The head of the ICRC in Colombia, Jordi Raich, confirmed their release in a press conference Thursday, saying one of the freed men has difficulty walking.

"One of them has problems with mobility," Raich said, adding that the others are "generally in good condition."

"Civilians" handed over the four Chinese men Wednesday night in the same area where they were taken captive on June 8, 2011, the Red Cross officials said.

It is not the Red Cross' mission to investigate who was responsible for the kidnappings, but only to mediate to secure the captives' release, Raich said.

China's ambassador to Colombia, Wang Wiaoyuan, told reporters that it remains unclear who was behind the abductions.

Earlier Thursday, the National Police attributed the kidnappings to the Revolutionary Armed Forces of Colombia, or FARC, guerrilla group, while Deputy Defense Minister Jorge Enrique Bedoya accused the rebels of having a "double standard," apparently alluding to the insurgents' pledge in February to halt the practice of kidnapping for ransom.

The Colombian government and the FARC launched the second phase of their peace talks on Monday in Havana with a negotiating session that began with discussion of the concentration of land ownership in the Andean nation.

The start of the meeting was preceded by the announcement by the FARC of a unilateral cease fire lasting from Nov. 20 until Jan. 20, 2013.

The FARC has battled a succession of Colombian governments since 1964. The Marxist insurgency swelled to nearly 20,000 fighters in the early 2000s, but now numbers around 8,500 combatants.

Colombia's armed forces, bolstered by billions of dollars of aid from the United States, have scored dramatic successes against the FARC in recent years, but the rebels remain capable of inflicting significant damage on the military and on vulnerable infrastructure, including oil pipelines. EFE