A Roman Catholic bishop was beaten to death in Guatemala two days after presenting a scathing report on human rights violations during the country's 36-year civil war.

Auxiliary Bishop Juan Gerardi Conedera was dragged from his bed at his home in Guatemala City on Sunday night and killed by blows to the head, prosecutors said.Church sources said the murder weapon appeared to be a cement block, and that the killer entered the 75-year-old priest's residence through a garage door.

Prosecutors and church officials said Monday they have not determined a motive in the killing.

Gerardi was head of the Guatemala City archdiocese's human-rights office. A lay worker who helped Gerardi in the three-year human-rights probe said the timing of his killing was suspicious.

"We can't come to a conclusion yet," said Edgar Gutierrez, the head staffer on the report "Never Again in Guatemala," which Gerardi presented at the Guatemala City cathedral Friday.

But Gutierrez said "we can't ignore" the fact that the report - which blamed the Guatemalan army and civilian paramilitary groups it created for nearly 80 percent of rights abuses in the civil war - had just been released.

Jean Arnold, director of U.N. mission for Guatemala, called the killing "a violent contrast, given that Gerardi was a man who played a role in the peace process."

In one of Latin America's longest civil conflicts, leftist rebels fought the often repressive Guatemalan government, demanding land reform and greater democracy. A peace accord was signed in 1996.

Gerardi is the first bishop slain in Guatemala.