Catholic Church representatives in Kinshasa accused a brother-in-law of President Felix Tshisekedi of stealing church land, a move they decried as "state banditry".
"We have had the title of ownership" of this concession of about nine hectares since colonial times, said Father Christian Ngazin, rector of the major theological seminary of St John XXIII, west of Kinshasa.
In 2019 "a group of people" came to the land, part of a larger church plot which hosts a major seminary, and wrongfully claimed to own it, he added during a press conference at the contested site.
On Monday "they came, broke down the door, attacked the security guards and started construction work. They came under the mandate of Mr John Nyakeru," said Ngazin. "This is state banditry".
Nyakeru is the DR Congo's ambassador to Kenya and brother of Tshisekedi's wife Denise Nyakeru.
"This land has belonged to the archdiocese of Kinshasa since colonial times," said Cardinal Fridolin Ambongo, archbishop of Kinshasa, who was accompanied by the land titles registrar, mandated by the minister of land affairs.
Relations between the Congo's leaders and the influential Roman Catholic Church have been strained for decades.
Katako Okito, who presented himself as the lawyer for the opposing party, said the site in question was subdivided in 2019.
This mean "there are titles in the names of third parties and all of a sudden the Church considers that it belongs to it." he told AFP without naming his client.
"The land registry is there, the justice system is there, if the church feels (wronged) it can go to court against my clients," Okito said.