Brazilian President Luiz Inacio Lula da Silva said on Thursday he would personally lobby Nicaragua's Daniel Ortega to release a bishop who has been imprisoned in the Central American state.

Speaking to reporters a day after meeting Pope Francis, Lula said the Nicaraguan president should have "the courage" to recognize that a mistake had been made. "These things are not always easy because not everyone is big enough to apologise."

Bishop Rolando Alvarez, a vocal critic of Ortega, was sentenced to more than 26 years in prison in Nicaragua in February on charges that included treason, undermining national integrity and spreading false news.

"I intend to speak with Daniel Ortega about this to release the bishop. There is no reason for the bishop to be prevented from exercising his function in the Church," Lula said.

It was not clear if Francis had asked Lula to intervene and seek to alleviate the most acute crisis the Roman Catholic Church faces in Latin America.

"The only thing the Church wants is for Nicaragua to free them," Lula said, referring to Alvarez and a number of detained priests.

While Brazil and Nicaragua have good relations, ties between the Vatican and the Central American state have been severely strained following a crackdown on anti-government protests in 2018, when the Church acted as a mediator between both sides.

Ortega called the protests an attempted coup against his government. The Church had called for justice for more than 360 people who died during the unrest.

Alvazez was convicted after he refused to leave the country along with 200 political prisoners released by Ortega's government and sent to the United States.