El Salvador said on Saturday it had detained four former soldiers accused of killing six Jesuit priests during the country's civil war, and would keep searching for 12 other suspects who remain at large.
In January, the government said it would help arrest former soldiers linked to the 1989 killings after a Spanish judge sent a new petition for the soldiers' arrest to the international police agency Interpol.
The four were captured in a Friday night operation. Another member of the group is facing extradition to Spain from the United States.
Prosecutors say Salvadoran soldiers shot the priests at their home at a university to silence their criticism of rights abuses committed by the U.S.-backed army during the 1980-1992 civil war, which claimed an estimated 75,000 lives.
Spain's High Court ruled in 2011 that the ex-soldiers should be tried for the killings and ordered them arrested. Interpol also said the men were wanted for extradition. But El Salvador's Supreme Court ruled at the time that Interpol had required the soldiers be located but not arrested or extradited.
The crime is one of the most emblematic of the armed conflict that pitted the then-leftist guerrillas and now ruling party Farabundo Marti National Liberation Front (FMLN) against the Salvadoran army.