ASUNCION, Paraguay (AP) — Paraguay's president canceled his trip to a climate conference after an attack by suspected leftist guerrillas killed a police officer and three laborers at a farm in the South American nation's north.

A statement from the presidential press office late Wednesday said President Fernando Lugo would not attend the Global Peoples Conference on Climate Change being hosted by Bolivia's leftist president, Evo Morales.

Deputy Interior Minister Carmelo Caballero blamed the farm attack on the Paraguayan People's Army, a leftist group that has been linked to bank robberies and kidnappings in the past decade. He said guerrillas apparently were trying to steal animals.

Caballero said Lugo had ordered troops sent to the area to bolster the police and was discussing with the Cabinet the possibility of declaring a state of emergency in the Concepcion region.

The rebel group has been a political thorn for the left-of-center Lugo, who before becoming president was a Roman Catholic bishop who championed liberation theology and its message of social change to help the poor.

Some of the president's critics on the right argue that Lugo's preaching encouraged the rebel group, while his supporters deny that and call the guerrillas dangerous. Some on the left, meanwhile, have criticized Lugo for sending special forces to hunt for the guerrillas.