Colombia's FARC rebels killed a policeman and a child with a grenade in what the defense minister called a "demented, diabolical'' attack and police said the guerillas also blew up an oil pipeline.
Fighting has intensified since a unilateral FARC ceasefire expired on Jan. 20, with guerrillas taking hostages, killing soldiers and blowing up oil and energy infrastructure and government security forces also stepping up operations.
The violence comes even as the two sides talk peace in Havana to try to end a five-decade-long war that has killed tens of thousands of people and displaced millions more.
Defense Minister Juan Carlos Pinzon said the FARC, or the Revolutionary Armed Forces of Colombia, killed a policeman and a boy in a village in the southeastern province of Guaviare on Monday night while residents tried to put out a fire the rebels had started.
"This act is demented, diabolical, there's no other explanation,'' Pinzon told journalists on Tuesday.
"In whose mind does it make sense to throw a grenade at a group of people, police and citizens who are working shoulder to shoulder to put out a fire? ... In what war, under what logic is that acceptable? None.''
In a separate attack in the southern Putumayo department, the guerrilla group blew up a pipeline, police said. It was not immediately clear which line was attacked.
President Juan Manuel Santos' administration and the FARC's leaders launched a peace process late last year, the latest in a long history of failed attempts.
On Sunday, the government and the Marxist rebels said their talks were picking up in pace and making progress toward an agreement on land reform, the first in a five-point agenda.
A U.S.-backed military offensive against rebels and drug gangs since 2002 has made vast strides in improving security in Latin America's No. 4 oil producer, opening up swathes of the country to investment, especially in the oil and mining sectors.