More than 100 human rights defenders have been killed in Colombia this year, according to the United Nations, which urged more accountability and better protections.

Activists have been particularly at risk in regions that were vacated by rebel fighters under a peace agreement signed last year, leaving a power vacuum, the UN’s human rights office in Colombia said in a statement.

The peace accord signed by the Colombian government and the Revolutionary Armed Forces of Colombia (Farc) ended a civil war that had lasted half a century.

More than half of the 105 rights activists and community leaders killed this year were gunned down by hitmen, the UN said.

By comparison, in 2016, 127 rights defenders and community leaders were killed, up from 59 in 2015 and 45 in 2014, according to UN figures.

“The Office notes with deep concern the persistence of cases of killings of human rights defenders in the country,” the UN human rights office said.

“Cases of killings of male and female leaders and [rights] defenders have occurred in areas from which the Farc has left, and which has created a vacuum of power by the state.”

One victim was the community leader Luz Jenny Montano, 48, who last month was shot by men riding on motorbikes near her home in the town of Tumaco, along Colombia’s Pacific coast.

Local groups say community leaders who speak out against rights abuses and activists campaigning for land rights are targeted by organised crime groups who see the activism as a threat to their economic interests.

“The Office has reiterated that the prevention of attacks and aggressions against human rights defenders involves investigation, prosecution and punishment of those responsible,” the office said.

The UN refugee agency (UNHCR) has also sounded an alarm about the dangers faced by Colombia’s rights defenders.

Last month, the UNHCR said it was “more and more worried” about the rise in killings and threats against rights activists along Colombia’s Pacific coast.

Most victims belonged to Afro-Colombian and indigenous groups, it said.

Earlier this week, the defense minister, Luis Carlos Villegas, said authorities are working to bring those responsible to justice.

Across the Americas, rights activists are being increasingly targeted, the UN has said.

Last year, three out of four recorded murders of human rights defenders worldwide took place in the Americas, it said.