Supporters of late Spanish dictator Francisco Franco marked the 35th anniversary of his death

Supporters of late Spanish dictator Francisco Franco marked the 35th anniversary of his death Saturday by praying outside the basilica that houses his tomb, barred from attending a mass inside due to repair works.

About 100 anti-Franco demonstrators also later gathered outside at the Valley of the Fallen near Madrid, calling for the site's 150-metre-tall (500-foot) granite cross to be torn down and the general's remains moved elsewhere.

The protesters from the Forum for Memory, dedicated to identifying killed or missing opponents of Franco, shouted "We will not forget", a reference to Franco-era crimes.

"The Valley of the Fallen is a horror whose persistence in the heart of the country is inconceivable," the forum said in a statement.

The state-run Patrimonio Nacional, keeper of some of Spain's grandest historic houses, has since April blocked access to the sprawling site, citing public safety risks from repairs on buildings there.

The Benedictine community which oversees the basilica on Saturday celebrated a mass inside for members of the order to mark Franco's death on November 20, 1975.

More than 100 Franco supporters prayed outside the gates, chanted "Long Live Spain" and "Long Live Franco" and raised right-wing salutes.

Some wrapped themselves in the former Spanish flag from the Franco era, which is adorned with an eagle, a symbol that was changed after the dictator's death and replaced with the royal Bourbon coat of arms.

They were separated from the anti-Franco protesters by dozens of police, and there were no incidents.

The Valley of the Fallen, a vast underground mausoleum, was built on Franco's orders between 1940 and 1958.

Historians estimate the mass graves contain the remains of between 40,000 and 60,000 Franco supporters and the Republicans who opposed them in Spain's 1936-39 Civil War, which led to Franco's rise to power.

But for many Spaniards, the memorial site -- carved into the side of a mountain in part through the forced labour of political prisoners -- is their country's most divisive and potent reminder of the Franco era.

It drew gatherings of far-rightists nostalgic for Franco's rule until a law passed in 2007 by the socialist government of Prime Minister Jose Luis Rodriguez Zapatero outlawed political rallies there.

The Franco Foundation, run by the late dictator's daughter Carmen, claims the government is using the excuse of danger from repair work to prevent masses for Franco at the basilica, consecrated by Pope John XXIII in 1960.