As Colombians rang in a new year without war for the first time in a half-century, tension and uncertainty were mounting in several rural areas affected by the armed conflict amid reports of a surge in killings of leftist community leaders, social activists, and members of the Patriotic March party.

At least 58 activists were killed in 2016, according to official government data. However, the United Nations placed the figure at 61, and the National Indigenous Organization of Colombia estimated that there were as many as 94 assassinations. The violence surged toward the end of the year as the government was finalizing a revised peace accord with the Revolutionary Armed Forces of Colombia (FARC), according to the Washington Post.

The killings have taken place in half of Colombia’s 32 departments, stoking fears among activists of a coordinated extermination campaign against leftist leaders reminiscent of attacks carried out by paramilitary forces in the 1980s against the Patriotic Union party, which resulted in the deaths of some 3,000 of the party’s members, including two presidential candidates.

For its part, the Colombian government has rejected the comparison and insists that there is no evidence that the recent killings are systematic or designed to undermine the implementation of the peace accord with the FARC.

“The government has not found that these crimes are systematic (but) without a doubt, they worry the government of President Juan Manuel Santos,” Interior Minister Juan Fernando Cristo told Caracol Radio. He added that, “in these territorial disputes there are community leaders who oppose illegal mining, who work in the substitution of (illicit) crops, and are often killed by mafias or people who run the drug trade.”

Regardless of the motives, the killings underscore one of the immense challenges Colombia faces as it enters the post-conflict phase: How to guarantee security and bring the rule of law to rural areas of the country where governmental presence has long been lacking.

The spate of killings also come as the FARC prepare to withdraw from areas where the group has allegedly made millions of dollars from drug trafficking, illegal mining, and extortion schemes. Local residents fear that criminal gangs or other armed groups could fill the power vacuum the guerrilla leave behind. Cristo said at least some of the crimes have occurred in the areas the FARC have already pulled out from.

Santos, the FARC, and the international community have condemned the killings. In November, Santos met with human rights leaders in Colombia to devise strategies to end the violence. Attorney General Néstor Humberto Martínez designated 21 investigators to “take on the enemies of peace in Colombia.” So far, only four cases have been prosecuted, according to the U.N. Office of the High Commissioner for Human Rights in Colombia.

“I summoned a high-level human rights commission to take action on crimes and aggressions against social leaders. Peace in Colombia cannot wait,” Santos later said on Twitter.

But the assassinations continued in December as the government continued laying the legal groundwork to implement the peace accord.

On December 28, Congress passed an amnesty law that will protect thousands of guerrillas who committed minor crimes during the war from prosecution. Rebels who committed war crimes or human rights violations — including massacres, kidnapping and sexual violence — will not be protected by the law.

By January 30, the number of FARC rebels who do not qualify for amnesty will be decided, the government and FARC said in a joint statement. An estimated 7,000 FARC rebels are expected to begin turning over their weapons and demobilizing in the next four months.

Although the law passed unanimously, current senator and former President Álvaro Uribe and his Democratic Center party vehemently opposed the measure and abstained from voting.

And the stakes could not be higher for the fledgling peace accord. In December, the FARC expelled five commanders who opposed the peace process. “This decision is motivated by their recent conduct, which has brought them into conflict with our political-military cause,” the FARC said in a statement.

The commanders allegedly operated in the Amazonian department of Guaviare. Around 300 FARC members have deserted the established gathering areas in Guaviare, sources told El Tiempo in December. The expulsion raised fears that some rank-and-file guerrillas, who already distrust the Colombian government, might lose faith in the peace process, refuse to demobilize, and form other armed groups.

Minister of Defense Luis Carlos Villegas has suggested that the military will crack down on FARC rebels who refuse to demobilize. “Those who declare themselves as dissidents of the FARC or simply become bandidos in search of money, gold, and dollars are high-value objectives,” Villegas told El Tiempo. “We are going to pursue them.”

By mid-January, the FARC are scheduled to relocate to the 27 concentration areas that will be monitored by the United Nations and delegates from several countries. By April, according to the timeline presented, the FARC will have turned over its weapons and demobilized.

Santos, in his end-of-the-year address on December 31, told Colombians that despite the historic achievements of 2016, many challenges still lie ahead.

“The challenges continue to be immense,” Santos said. “But the spirit, the talent, and the perseverance that characterize us will allow us to face them with optimism and faith in the future … The main challenge we Colombians have for the year that begins tomorrow is, without any doubt, reconciliation and peace building.”