Czech police said Friday they had recovered the skull of Saint Zdislava of Lemberk, a 13th-century saint revered for her charitable work, days after it was stolen from a church in northern Czechia by a man who allegedly planned to bury the relic in a river after encasing it in concrete.

The skull, believed to be around 800 years old, was taken Tuesday from a glass shrine inside the Basilica of Saint Lawrence and Saint Zdislava in the town of Jablonne v Podjestedi shortly before Mass, when the church alarm system was turned off.

Police detained a 35-year-old man on Thursday in the city of Mlada Boleslav following what regional police chief Petr Rajt described as "meticulous police work and a bit of police luck."

Authorities said the suspect admitted to stealing the relic because he opposed its public display in the church. According to police, he intended to cover the skull in concrete and sink it in a river as a private burial.

"We know he wanted to sink it in the river today to bid farewell in this way," Rajt told reporters. "If we had failed to detain the man yesterday, the skull would probably never be found."

Police said the relic had already been encased in concrete when it was recovered, leaving restoration experts with the difficult task of extracting and preserving it.

Rajt said the suspect prayed to be alone in the church before carrying out the theft.

"He prayed to God that he would be alone in the church – and that's what happened," Rajt said. "But he was obviously so determined to commit the crime that there was nothing to stop him."

Detective Jan Ujka said the man, who has no prior criminal record, pleaded guilty and was charged with theft and related offences. He faces up to eight years in prison if convicted and is now in pre-trial custody.

Saint Zdislava of Lemberk, who lived from around 1220 to 1252, was a Bohemian noblewoman known for caring for the poor and sick. She was canonized by Pope John Paul II in 1995.