BOGOTA - Gunmen have shot and killed at least 12 Awa indigenous natives, four of them children, in an attack in a southern coastal region of Colombia that is a springboard for cocaine shipments.

Wednesday's attack near the Ecuador border was carried out by "hooded men wearing military uniforms" at the Gran Rosario reserve, 80 kilometers (50 miles) from the Pacific port of Tumaco, said National Indigenous Organization of Colombia (ONIC) president Luis Evelio Andrade.

Some 11,000 members of the Awa indigenous group occupy a strip of land along the border region that is also used by drug traffickers to facilitate cocaine shipments across the Pacific.

"In that zone, guerillas, paramilitaries and the army are active," said Andrade, whose group represents 1.3 million Colombian native Indians.

The Colombia office of the UN High Commissioner for Human Rights, which has reported increased attacks by armed groups on indigenous groups, "strongly" condemned the latest killing in a statement.

President Alvaro Uribe's government said it "repudiated and condemned" the murders and offered a reward of about 50,000 dollars for any tips leading to the arrest of the perpetrators and instigators.

The United Nations attributes most of the 63 murders of native Indians this year to the left-wing Revolutionary Armed Forces of Colombia (FARC), Latin America's oldest and largest rebel group.

The Awa, in turn, say they are being targeted by a campaign of extermination for their decision to remain neutral in the Colombian conflict pitting FARC guerillas against Uribe's conservative government.

Since early this year, about 1,700 Awa have been living in four makeshift shelters in the towns of Altaquer and Ricaurte in Narino state, after leaving their homes following a series of murders by FARC guerillas.

In April, FARC leader Alfonso Cano apologized to the Awa in a public letter, after admitting that rebels killed eight members of the native group for alleged collaboration with the Colombian army.

Narino ombudsman Carlos Maya told AFP that violence in the border region has spiked in recent years due to its strategic location where drug traffickers and armed groups are present, with natives often caught up in the crossfire.

Cocaine trafficking has gradually shifted in recent years toward the Pacific Ocean, which is less secure and guarded than the Caribbean Sea.