NAIROBI (Reuters) - Swearing in an alternative president of Kenya would be an act of treason, the country’s attorney general said on Thursday, days before an opposition leader expects to be inaugurated by an unofficial people’s assembly.

Kenya's Attorney General Githu Muigai speaks during a press conference in Nairobi, Kenya September 22, 2017. REUTERS/Baz Ratner

Such an inauguration would worsen the rifts opened by an acrimonious election season, when more than 70 people died in political violence. The extended campaigns eventually led to President Uhuru Kenyatta’s re-election.

Attorney General Githu Muigai did not name anyone, but opposition leader Raila Odinga said last month that he would be inaugurated by a people’s assembly on Dec. 12 - Kenya’s Independence Day.

Unless a candidate was declared the victor in an election by the Independent Electoral and Boundaries Commission and the swearing-in was conducted by the Kenyan chief justice, Muigai told a news conference, such a inauguration is “a process wholly unanticipated by the constitution and is null and void”.

“The criminal law of the Republic of Kenya stipulates that sort of process is high treason,” he said. “It is high treason of the persons involved, and any other person facilitating that process.”

Under Kenyan law, treason is punishable by death.

Muigai said people’s assemblies proposed by the National Super Alliance, Odinga’s opposition coalition, were illegal as well.

“These institutions are unconstitutional they are illegal, they are null and void. The persons involved in their creation are involved in extra-constitutional activity and may be visited by the full force of the law,” he said.

So far, 12 Kenyan counties have passed motions supporting the formation of a people’s assembly, most of them counties that had backed the opposition in Kenya’s protracted voting.

Odinga and Kenyatta faced off in an election in August that Kenyatta won. But the Supreme Court nullified the result, and a repeat election was held on Oct. 26. Odinga boycotted that vote, saying reforms needed to avoid “illegalities and irregularities” had not been made. Kenyatta won again, with 98 percent of the vote.

The United States had urged opposition leaders to work within the law and avoid actions like the proposed “inauguration ceremony”, a statement from the U.S. Embassy in Nairobi said on Wednesday, following a visit to Kenya by Donald Yamamoto, the acting assistant secretary of state for African affairs.

Without directly mentioning the ceremony or the United States, Odinga said on Thursday that Kenyans should be left to solve their own problems.

“Our friends can give us advice ... in privacy. Don’t come and shout at us, and tell us that we are going to violate the constitution. Which constitution, my foot,” Odinga told reporters in Nairobi.