Colombian rebels firing homemade mortars killed at least eight police officers and wounded four others in a pre-dawn attack on a police barracks.

Two police officers were missing after the attack, near the Ecuador border, on a barracks housing 80 police in the town of San Miguel, said the minister, Rodrigo Rivera.

FARC (Las Fuerzas Armadas Revolicionarias de Colombia - the Revolutionary Armed Forces of Colombia) rebels have for years used Ecuador as a refuge, crossing the San Miguel river to attack Colombian forces.

Rivera immediately made contact with Ecuadorean officials to discuss the possibility that it had happened again.

The FARC and Colombia's number two rebel group, the ELN (National Liberation Army - Ejercito de Liberacion Nacional) have stepped up attacks on security forces since President Juan Manuel Santos took office on 7 August, 2010.

At least 28 police officers and soldiers have been killed, 17 in the past week.

Santos is defiant, claiming those responsible "are dead wrong if they think that attacks like these will weaken us. On the contrary, it fills us with determination, because we will not rest, not for a second, until we have peace in this country."

Santos was defence minister under his predecessor, Alvaro Uribe, who weakened the rebels with billions of dollars in US military aid but many analysts believe the rebels cannot be defeated by arms alone.