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Colombian Defence Minister Rodrigo Rivera has been meeting the heads of the army and the police in an effort to curb attacks by the country's biggest left-wing guerrilla force, the Farc.

The meeting followed the deaths of six soldiers on Thursday.

Two were killed in fighting with the rebels near the western city of Cali, and four died in eastern Meta province.

On Monday, Colombian President Juan Manuel Santos set out new strategies against the rebels.

He said improved intelligence-sharing and smaller, more flexible units were needed to take on the rebels.

"I've ordered the defence ministry to revise the way the (army) controls territory, including our borders, to use our forces more efficiently and effectively," President Santos said.

Rodrigo Rivera held a meeting on Thursday with Deputy Commander of the Colombian Police Gen Rafael Parra and army head Gen Alejandro Navas to discuss the new tactics.

Guerrilla war

The security forces have lost an increasing number of their men in grenade and mine attacks.

Twelve soldiers had to be airlifted out of a mine field in Vista Hermosa, in Meta province, on Thursday.

Four more were injured by grenades in a mountainous area near Jamundi, in Valle del Cauca.

And in June, the Commander of the Transport Police in Antioquia was killed in an ambush.

The government says the rebels are reacting to increased pressure from the security forces in a bid to survive.

President Santos said they were increasingly dressing as civilians to merge into the general population and carrying out small-scale attacks for maximum attention but little risk to themselves.

There have also been reports of the rebels stuffing footballs with explosives and dropping them from trees when patrols pass underneath.

The president said the security forces would have to adjust their doctrine, their operations and their procedures to the way the rebels were operating.