BOGOTA -- The rights group Amnesty International said Thursday that Colombian right-wing paramilitary groups responsible for massacres of civilians have acted with the complicity of certain sectors of the military.

Amnesty's regional director for Latin America, Javier Zuniga, told a press conference that in certain regions of Colombia there is so little attempt to hide the complicity that football matches have reportedly been organised between paramilitaries and the military.

An Amnesty researcher for Colombia, Susan Lee, told AFP that the paramilitary groups are "without doubt responsible for the worst human rights violations in Colombia."

Paramilitary groups were responsible for around 70 percent of massacres reported this year in Colombia, which total 290 separate incidents, she said.

Leftist guerrilla groups were responsible for about 25 percent of massacres reported so far in 1999, and the remaining 5 percent are believed to have been committed by Colombia's security forces, Lee said.

A delegation from the London-based human rights organisation has been on a fact-finding visit to Colombia this week. Amesty closed down its Bogota office in 1997 after its staff received repeated death threats.

For decades, right-wing paramilitary groups such as the Self-Defense Units of Colombia (AUC) have clashed with leftist rebels of the Revolutionary Armed Forces of Colombia (FARC) and the smaller National Liberation Army (ELN).