By JUAN FORERO
 
BOGOTÁ, Colombia, Dec. 10 - Even as Colombian officials on Friday celebrated the disarmament of 1,400 right-wing paramilitary fighters in the Catatumbo region of northeast Colombia, rights groups and some lawmakers warned that the effort to demobilize the groups was moving too fast, with no verification of the results and no assurance it could bring lasting peace.

Officials hailed the effort in Catatumbo, which culminated in ceremonies in the region on Friday, as a major step toward ending the country's conflict and meeting the government's goal of disarming Colombia's 15,000 paramilitary fighters within a year.

But a respected local rights group in the Norte de Santander Province, which includes Catatumbo, says fighters with paramilitary death squads killed more than 300 people in the province in the year leading up to the demobilization, despite a cease-fire the fighters had promised two years ago after informal talks began. The rights group, the Progress Foundation, said that spate of violence has mocked the disarmament effort and raised the specter of future violence.

In a report in October, another rights group, the Colombian Commission of Jurists, said paramilitary groups had killed or caused the disappearances of 1,895 people nationwide from December of 2002 until this September.

The government's own human rights ombudsman also issued a report, in September, detailing murder, displacement, extortion and land seizures at the hands of the United Self-Defense Forces, the main paramilitary organization.

In Catatumbo, the fighters belong to militias under the command of Salvatore Mancuso, who has been convicted in absentia for murder and is wanted in the United States on drug trafficking charges. In a disarmament ceremony on Friday in the town of Tibú, Mr. Mancuso handed in a Beretta pistol and asked for forgiveness.

"With my soul flooded in humility," Mr. Mancuso said, his eyes tearing up, "I ask the pardon of the people of Colombia."

But for many villagers in the region, his words rang hollow. "What are these 1,400 men going to do now? What?" asked Isabel Obregón, whose husband, Tirso Vélez, was slain by paramilitary gunmen in July. "All they know is how to kill."

That concern is also held by rights groups and diplomats, who say that with no real independent verification process, the paramilitaries could regroup and continue to traffic drugs and take aim at their enemies.

In an effort to erode support for Marxist rebels and control the booming drug trade, the paramilitaries entered the Catatumbo region, which borders Venezuela, in the 1990's. The rebels hit back, planting land mines, striking debilitating blows against the invaders and killing civilians.

Under this spiraling violence, the paramilitary groups have started to disarm in stages around the country, with the demobilization on Friday the largest since the first disarmament in November 2003.

But diplomats, rights groups and some members of Congress here say the government is moving too quickly, allowing killers to disarm without having a legal framework in place to investigate and try them.

"After 1,400 paramilitaries demobilize, who can guarantee that they will not continue to exert control as civilians, supported by the vast illegal empire that they built with the narcos?" Colombia's leading newspaper, El Tiempo, asked in an editorial on Thursday.

Until now, the paramilitary groups have shown little inclination to stop killing. Ms. Obregón said that in the case of her husband, the fighters took aim at him because of his leftist leanings.

"They killed all kinds of people, leaving widows and refugees," she said. "What kind of peace is this?"