DAKAR (Reuters) - The U.N. mission in Central African Republic has fired one of its lawyers after he accused Rwandan peacekeepers of massacring 30 civilians in the capital last month and said they could be investigated.

FILE PHOTO: A general view shows part of the capital Bangui, Central African Republic, February 16, 2016. Picture taken on February 16, 2016. REUTERS/Siegfried Modola/File Photo

Juan Branco signed on with the U.N. mission, known as MINUSCA, on May 15 to advise a new Special Criminal Court charged with investigating war crimes and crimes against humanity.

The Franco-Spanish lawyer has previously represented Julian Assange, founder of the WikiLeaks site.

The court backed by the United Nations is due to begin formal investigations next week despite questions about how effective it can be when the government does not control vast swaths of the conflict-ravaged country.

In a letter dated May 28 and provided by Branco to Reuters on Thursday, MINUSCA’s human resources department told Branco that tweets he wrote after signing his contract violated a prohibition against actions “that may adversely affect the interests of the United Nations”.

“The consultant agreed and acknowledged ... that any breach of any of the provisions of the contract shall constitute a breach of an essential term of the contract and gives rise to grounds for terminating the contract,” it said.

In one tweet, Branco wrote that Rwandan peacekeepers had “massacred more than 30 civilians and wounded 100 others without any justification”, referring to clashes on April 10 in the capital Bangui’s PK5 neighborhood.

The deaths infuriated local residents, hundreds of whom laid the bodies of at least 16 people in front of the entrance to the MINUSCA base. The United Nations said at the time the people they killed had been armed by criminal gangs.

Rwanda’s minister of state in the ministry of foreign affairs, Olivier Nduhungirehe, told Reuters that he was not aware of any such accusations against Rwandan peacekeepers.

“It sounds like that person is the kind of (person) who says whatever he wants, (which is) the reason why he is ... getting fired,” he said on Thursday.

In an email to a U.N. legal officer contesting his firing, Branco accused MINUSCA of trying to cover up a massacre.

He said the firing was motivated by a letter he wrote to the court’s special prosecutor and MINUSCA’s top judicial affairs officer the day before saying it was possible the court would investigate alleged crimes by U.N. peacekeepers.

In the email, which Branco also provided to Reuters, he denied that his contract restricted him from publicly expressing his opinions or that his actions ran contrary to the interests of the United Nations.

“Denouncing crimes, without breaking any confidentiality obligations, is a requirement for anyone, and in particular for those in charge of fighting them,” he wrote.

A MINUSCA spokesman said in a statement to Reuters that “commenting publicly about responsibility for crimes, even before he had arrived in the country, is behavior clearly unacceptable for someone contracted to aid in the operationalization of a special court”.

MINUSCA has more than 12,000 armed personnel deployed in Central African Republic, where hundreds of civilians have died since 2013 in conflict fought largely along religious lines and scores more have been raped and tortured.