Eight former Colombian rebels who once battled the government with rifles and bombs have been sworn into office.

The ex-combatants with the former Revolutionary Armed Forces of Colombia took their seats in congress for the first time on Friday, in another crucial step in implementing the country’s peace accord.

“This is a big responsibility we’ll be shouldering,” said Sandra Ramirez, the widow of a legendary guerrilla leader. “It’s a change from life in the mountains, from boots in the mud.”

The fledgling politicians represent a small faction in a Congress that has the task of pushing forward key aspects of the peace agreement.

The rebels were guaranteed 10 seats in the legislature as part of the accord, a stipulation that has angered many Colombians.

In his address to the new legislature, outgoing president Juan Manuel Santos acknowledged the hesitation of Colombians to embrace the former rebels as politicians, but said including them in politics was a powerful demonstration of democracy.

Colombia’s president Juan Manuel Santos speaks during the inauguration of the newly-elected legislatureColombia’s president Juan Manuel Santos speaks during the inauguration of the newly-elected legislature (AP Photo/Fernando Vergara)

“It fills me with satisfaction that those who for more than half a century fought the state and its institutions with arms today bow to the constitution,” he said.

The oath ceremony comes just weeks before conservative Ivan Duque assumes the presidency amid signs that the peace accord remains on shaky ground.

Mr Duque vowed throughout his campaign to modify important aspects of the agreement, though he has softened some of his positions since the polarising election.

Two of the former leaders of the disarmed Revolutionary Armed Forces of Colombia did not take their seats in Congress on Friday. Seuxis Hernandez remains jailed in Colombia on US drug charges while Ivan Marquez is holed up in a rural camp for former guerrillas, telling comrades he fears for his safety.

Colombia’s conflict between leftist rebels, paramilitaries and the state left at least 250,000 dead, 60,000 missing and millions displaced in a war that still haunts many.

Even as the number of homicides drops to a four-decade low, in many parts of the country drug traffickers and smaller illegal armed groups still wreak havoc. Since the signing of the accord, more than 300 social leaders and dozens of former rebels have been killed.

Carlos Lozada, right, and Sandra Ramirez, former members of the demobilized Revolutionary Armed Forces of ColombiaCarlos Lozada, right, and Sandra Ramirez, former members of the demobilized Revolutionary Armed Forces of Colombia (AP Photo/Fernando Vergara)

Many fear the wave of violence could portend a repeat of events in the 1980s, when dozens of leftist politicians affiliated with the Patriotic Union party were gunned down.

Ms Ramirez said the ex-combatants taking office on Friday were aware of the threats they face.

“It worries us immensely,” she said.

To prepare for life as legislators, she and her comrades took a crash course at a university that taught them about the role of congress, the various types of laws and how to introduce a bill.

They are calling their coalition the Group for Peace and plan to focus on implementing the accord and defending human rights. Among their first proposals are ideas to improve conditions for young children in remote, rural parts of the country and better guarantee access to water.

The former guerrillas face a steep challenge in winning over Colombians and exercising any pull in congress. They won less than 1% of the votes in the legislative elections and remain deeply unpopular in much of the country.