Brice Oligui Nguema, president of the Committee for the Transition and Restoration of Institutions (CTRI), was sworn in on Monday as Gabon's "transitional president" in the capital of Libreville.

The ceremony was held at the presidential palace, which is known as the "Renovation Palace."

"I solemnly and honorably undertake to do everything possible to achieve national unity. I swear," Nguema said before the constitutional judges.

A group of military officers last Wednesday appointed Nguema, commander-in-chief of the Gabonese Republican Guard, to head the transition in the name of the CTRI after starting a coup earlier in the day following the announcement of the re-election of President Ali Bongo Ondimba by the national electoral body.

The international community has voiced concerns over Wednesday's coup in Gabon. 

UN Secretary-General Antonio Guterres is following the situation in Gabon very closely, and notes with deep concern the announcement of the election results amidst reports of serious infringements of fundamental freedoms, said Stephane Dujarric, Guterres' spokesman, in a statement on Wednesday.

In a press statement, Chairperson of the African Union (AU) Commission Moussa Faki expressed great concern over the situation in Gabon and strongly condemned the coup attempt as a way to solve the post-electoral crisis. He called on all political, civil and military actors in Gabon to give priority to peaceful political avenues, and a rapid return to democratic constitutional order in the country.

China calls on relevant sides in Gabon to resolve differences peacefully through dialogue, Chinese Foreign Ministry spokesperson Wang Wenbin said on Wednesday, noting that China is closely following the developments in Gabon. "We call on relevant sides in the country to proceed from the fundamental interests of the nation and the people, resolve differences peacefully through dialogue, restore order at an early date, ensure the personal safety of President Ali Bongo Ondimba and safeguard the larger interests of national peace, stability and development," Wang added.

(With input from Xinhua)