Fighting between government troops and left-wing rebels in northern Colombia has left more than 70 people dead, according to the authorities

In some of the worst fighting since the peace process began, at least 39 soldiers, more than 20 guerrillas, four paramilitaries and 10 villagers have been confirmed dead.

The fighting began on Monday as a 500-strong column of the Revolutionary Armed Forces of Colombia, or FARC, tried to penetrate the area of Nudo de Paramillo - a right-wing paramilitary stronghold in the mountains of Cordoba province.

The first action was on four hamlets in northern Cordoba, where the rebels killed 10 villagers whom they accused of collaborating with the paramilitaries.

Army defeat

On Tuesday, Colombian troops poured into the area and soldiers from the 11th brigade were caught in a FARC ambush, suffering up to 40 casualties - the worst army defeat this year.

The army said its troops had killed 23 guerrillas in that action.

Paramilitary forces of the outlawed Self-defence Forces of Colombia also got involved against the guerrillas, in a region long considered one of their heartlands.

This is the second time the FARC have attacked Nudo de Paramillo. In December, another rebel column managed to reach the mountain fortress of paramilitary warlord, Carlos Castano, who narrowly escaped with his life.

The FARC killed and mutilated 30 villagers from the area in that action, determined to gain revenge for the activity of right-wing death-squads who have killed hundreds of left-wing sympathisers in massacres all over the country.