Madrid  - A judge at Spain's National Court has requested information on mass graves to determine whether he is competent to investigate disappearances during the 1936-39 Civil War and the subsequent dictatorship of General Francisco Franco, judicial sources said Monday.

Judge Baltasar Garzon requested information on disappearances from municipalities, parishes, administrative archives and the Valley of the Vallen, Franco's mausoleum near Madrid, which was built by political prisoners.

Garzon is trying to determine the number of Franco opponents who disappeared in reprisals, prisons and labour camps during and after the war.

An uprising led by Franco sparked the Civil War between his right- wing nationalists and the leftist republican government.

Franco won the war, ruling Spain until his death in 1975.

Families of his victims, which have lodged eight complaints at the National Court, say about 30,000 people disappeared.

The so-called Law of Historic Memory adopted in 2007 sought to do justice to Franco's victims with measures such as the removal of Francoist monuments.

Citizens' associations have exhumed the remains of hundreds of republicans from mass graves. (dpa)