UNITED NATIONS - UN Secretary-General Ban Ki-moon on Sunday condemned the rebels' seizure of state power in the Central African Republic (CAR), calling for "the swift restoration of constitutional order".

"The secretary-general condemns the unconstitutional seizure of power that took place in the Central African Republic (CAR) on 24 March 2013 and calls for the swift restoration of constitutional order," said a statement issued here late Sunday.

Rebels have seized control of Central African Republic's capital Bangui after President Francois Bozize fled the presidential palace, reports said Sunday.

The seizure of Bangui is the most significant step yet for the rebellion by guerrillas who call themselves Seleka, which is the word for alliance in the Sango language.

The secretary-general "reiterates that the Libreville Agreements, negotiated by the heads of state and government of the Economic Community of Central African States (ECCAS), remain the most viable framework to ensure durable peace and stability in the country", said the statement.

Seleka launched a lightening blitz this week after giving the government a deadline to honor a peace deal signed in January to release political prisoners, integrate rebels into the national army and pull out South African and Ugandan troops deployed in the country to protect the Bangui-based government.

The rebels opened a second front northwest of Bangui after capturing Bossembele, while the bulk of Seleka fighters claimed control of Bossangoa and Damara, 75 km from Bangui, which had been seen as a "red line" before the signing of the Libreville accord.

There were no reports of resistance when rebels overran both towns in the past days, despite the deployment of troops from the CEEAC between Bangui and Seleka fighters.

Seleka launched an insurgency on Dec 10, 2012, accusing Bozize of failing to implement a series of peace accords signed in Libreville since 2007.

With the mediation of regional countries, the rival sides again went to Libreville on Jan 11 to sign another agreement to end the crisis, under which Bozize, who came to power in 2003 in a military coup, will have no part in the next presidential election while allowed to finish his current term of office.

"The secretary-general is deeply concerned by reports of serious violations of human rights," the statement said. "He underscores that those who are responsible for committing such violations will be held accountable."

"The secretary-general appeals for calm and for the respect of the rule of law in the CAR," the statement said. "He is concerned by the dire humanitarian situation in the country and the reports of ongoing looting in the capital, Bangui, including of United Nations property."

"The United Nations is taking all precautions to protect its staff and reminds the authorities of their obligations to ensure the safety of all United Nations personnel and premises," the statement said.

"Through the special representative of the secretary-general for the Central African Republic, the United Nations will continue to work closely with its partners, including ECCAS and the African Union in joint efforts to help resolve the crisis in the Central African Republic," the statement added.