An anarchist group has claimed responsibility for a thwarted attempt to set off a bomb at Madrid's La Almudena Cathedral, Spanish police sources told Efe Friday.

The aim of Thursday's foiled strike was "to damage the Borbon monarchy in one of its sacred places," the self-proclaimed Mateo Morral Insurrectionist Commando said in a statement posted on the Internet.

La Almudena lies near the spot where anarchist Mateo Morral tried to kill King Alfonso XIII - grandfather of the current Spanish monarch, Juan Carlos - and Queen Victoria Eugenia on the occasion of their May 31, 2006, wedding.

Though the royal couple escaped unhurt, Morral's homemade bomb killed 30 people. Trying to flee, he was eventually recognized and surrendered to police, but later killed the officer guarding him before turning the gun on himself.

Thursday's bomb was spotted by a priest as he exited the confessional. He quickly cleared the cathedral of worshippers and tourists and contacted authorities.

Members of the police bomb unit, Tedax, defused the device without incident.

The rudimentary bomb contained 1,200 grams of gunpowder, a small cylinder of butane, a kilo (2.2 pounds) of metal screws and a alarm-equipped watch, police said.

"We demonstrate that your sanctified lairs are vulnerable," the Morral commando said.

Authorities have been concerned about a resurgence of anarchist movements as Spain suffers with recession and an unemployment rate above 26 percent, police sources acknowledged to Efe. EFE