Colombia has stepped up its offensive against FARC rebels, killing 21 in only three days, though the government on Tuesday defended peace talks still under way in Havana.

"The military offensive (against the guerrillas) continues at full strength until we reach agreements, as if there were no negotiations at all," President Juan Manuel Santos said on a visit to Madrid.

Colombian army troops killed at least seven FARC guerrillas Tuesday in an operation in the central department of Tolima, the military said.

The latest fighting comes after 14 guerrillas were reported killed over the weekend in an army air and ground assault on a rebel base in a rural area near the Venezuelan border.

Spanish police said Tuesday they had arrested a suspected Colombian hitman nicknamed "El Nino" (The Kid), accused of killing and then cutting up two compatriots whose remains were found in a Dutch canal.

The 33-year-old man is accused of murdering the two Colombian residents of Spain, whose chopped-up body parts turned up May 31 last year in a canal in the town of Pijnacker Nootdorp, near The Hague, Spanish police said in a statement.

The Colombian military said Monday a weekend offensive against the FARC killed 14 rebels, five more than previously reported.

The air and ground attack targeted a FARC camp near the town of Tame, in a rural area near the border with Venezuela, it said in a statement.

At least nine Marxist FARC rebels were killed in a clash with Colombia's military even as peace talks are held between the two sides in Cuba, the army said Sunday.

The military operation took place in the northern town of Tame, near the border with Venezuela.

Colombian President Juan Manuel Santos said Friday he believes his government can reach a peace deal with leftist rebels this year, a day after a deadly bomb attack blamed on the guerrillas.

"I am convinced that if both parties continue to be willing, we are going to achieve peace -- a peace which will change this country," Santos said in a radio interview.

A motorcycle bomb attack blamed on Colombia's FARC rebels killed one person and wounded at least 25 after a local truce by the guerrillas ended, an official said Thursday.

The attack took place near a local government headquarters in the western municipality of Pradera, Mayor Adolfo Leon told the RCN radio station, noting that "of the 25 wounded, six are critical."

Colombia's FARC rebels called on Tuesday in peace talks with the government for the regulated cultivation and sale of illegal crops like coca leaf, opium poppies and marijuana.

Rebel negotiator Pablo Catatumbo unveiled the proposal before the start of a negotiating session dealing with drug trafficking, the industry that has long fueled Colombia's brutal civil war.

Colombia's largest guerrilla group Tuesday condemned a secret U.S.-Colombian program to target and kill rebel leaders as "crimes" in violation of national sovereignty.

The Washington Post disclosed the intelligence-sharing program in a report last month that credited it with a role in the killing in 2008 of longtime guerrilla leader Raul Reyes, who died in a Colombian airstrike and raid on a rebel camp in Ecuador.

At least 10 guerrillas from Colombia's leftist FARC rebel group were killed in a clash with the military, Defense Minister Juan Carlos Pinzon told reporters Thursday.

"It was a very significant blow" to the rebel group, Pinzon said, adding that one of the victims was Pedron Lain Parra, a regional commander who was a key confidant of Jorge Briceno, the FARC's military chief who was killed in 2010.