Four Chinese oil company employees held hostage since June 2011, allegedly by Colombia's FARC rebels, have been freed in southern Colombia, their embassy said Thursday.

"They released the four last night in the department of Caqueta. They are in good spirits," said the spokesman of China's embassy in Bogota.

The official said the identity of the kidnappers was still unknown. He confirmed that the four hostages -- three engineers and a translator -- are Chinese citizens.

President Juan Manuel Santos welcomed the news in a message on Twitter.

"I talked to the Chinese ambassador and want to celebrate the release of the four Chinese citizens. Kidnapping is not something that should be repeated again," the president wrote.

The four were turned over to representatives of the International Committee of the Red Cross in Caqueta by unidentified men who were dressed in civilian clothes and were not armed, the ICRC said.

They were then taken to the town of San Vicente del Caguan and from there were flown to Bogota aboard an aircraft leased by the Chinese embassy, the ICRC said.

"It's excellent news for the families of the freed people, after a long time of waiting and uncertainty," the head of the ICRC in Colombia Jordi Raich said in a statement.

The hostages worked for Emerald Energy oil company, a British based subsidiary of the Chinese group Sinochem.

They were traveling in car driven by a Colombian when they were kidnapped. The driver was released hours later.

Defense Minister Juan Carlos Pinzon charged that the four had been held since their kidnapping by the FARC, the leftist rebel group that is currently in peace talks in Havana with the Colombian government.

"The FARC once again shows its true face: the face of a lying and traitorous organization," said Pinzon.

"After announcing with bells and whistles that they did not have a single hostage, today we can confirm that the FARC turned over to the Red Cross four Chinese citizens who have been kidnapped since June of last year," he said.

National Police chief Jose Roberto Leon Riano said the Colombian government provided "humanitarian assistance" at the request of the Red Cross but gave no details of the government's role in the release.

The Revolutionary Armed Forces of Colombia, Latin America's largest rebel group, has just begun peace talks with the government aimed at ending their decades-long conflict.

Earlier this year the FARC announced they would stop abducting civilians, whose ransoms had helped fund the group's activities.

In early April, FARC rebels freed 10 policemen and soldiers and said they were holding no more hostages.

But victims' associations in Colombia claim the rebels still hold a number of captives.