The Colombian government is blaming FARC rebels for a massive landmine explosion and subsequent fighting that has claimed the lives of seven soldiers.

The blast erupted Saturday in Tolima province, a long-time stronghold of the leftist Revolutionary Armed Forces of Colombia, known as FARC.

Tolima province, about 150 kilometers southwest of the capital Bogota, is where FARC began operations more than 40 years ago, and the area recently has seen a sharp increase in fighting between government security forces and FARC guerrillas.

The FARC, Colombia's largest rebel group, has killed nearly 600 members of the country's state security forces during the past year. The rebels' landmines also have caused heavy civilian casualties, many of them children from poor farming communities who trigger the hidden explosives by accident while walking to school.

Colombia has increased the number of military and police teams hunting for FARC members, and the guerrillas in turn have switched tactics instead of confronting security forces openly, the rebels now concentrate on planting landmines and explosives to disrupt government patrols.