The death of a 15-year-old boy after he was shot in the chest in the northwestern city of Leon raised the death toll from the crisis in Nicaragua to at least 155 people.

The Catholic Church on Thursday mourned the death of a young 15-year-old altar boy, who fell victim to a surprise attack by "paramilitaries" of the government.

"The message that has just arrived has made me cry, God has welcomed Sandor Dolmus, an altar boy murdered today by paramilitaries in Leon, to the altar of heaven," said Bishop Silvio Baez on his social network account.

The altar boy was with other children and neighbors, when the paramilitary group left the headquarters of the ruling Sandinista National Liberation Front (FSLN) and sprayed bullets at them, priest Victor Morales of the diocese of Leon told reporters.

The young man was shot in the chest with a high-caliber firearm and died a few minutes later, the priest said.

Dolmus was an altar boy at the Cathedral of the Assumption of Mary in Leon, classified as a World Heritage Site by the United Nations Educational, Scientific and Cultural Organization (UNESCO).