ALGIERS, Algeria (CNN) -- Even as United Nations officials continued a fact-finding mission in violence-plagued Algeria Sunday, at least 20 people were reported killed in two massacres blamed by the government on Islamic militants.

Security forces said Islamic fundamentalist rebels stormed the village of Khelil, about 275 miles (440 kilometers) west of Algiers, killing 12 people and wounding two. Another massacre was reported in Sidi Abdelmoumen, about 206 miles (330 kilometers) southwest of the capital, where eight victims' throats were cut.

Interior Minister Mustapha Benmansour visited Khelil, and security forces were mobilized early Sunday to search for the attackers.

Since 1992, an estimated 80,000 people have been killed in violence triggered when Algeria's military-backed regime nullified elections that a fundamentalist political party, the Islamic Salvation Front, was poised to win.

A six-member U.N. team, led by former Portuguese President Mario Soares, is in Algeria, holding extensive meetings with government leaders, security officers, heads of opposition parties, newspaper editors and representatives of diplomatic missions.

"Every day, we receive demands from many parties [for meetings,] so we'll take our time," said Soares, responding to reports that the team could be in Algeria for two more weeks.

Sunday, Soares and his team met with leaders of three opposition parties. They had previously met with human rights activists and Lt. Gen. Mohammed Lamari, the military's chief of staff.

Damage from the violence in 1995

While the government blames Islamic militants for the bloodshed, human rights activists told U.N. team members that security forces could be responsible for the disappearances of as many as 18,000 people since 1994.

The government has allowed the U.N. team to meet with some opposition political figures and has pledged to give it access to all necessary information. However, it is considered unlikely that the U.N. representatives will be allowed to meet with representatives of the Islamic Salvation Front.

Members of the U.N. team have not commented on their meetings so far. But one source said the panel has been asking tough questions about the massacres and was not staying away from controversial topics.

"We want this mission to be as objective as possible. The situation is very complex. That's why we must be prudent," said Soares.