Belgium's new government was sworn in by King Albert II on Tuesday at a ceremony at the royal palace that brought an official end to a world record-breaking 18-month crisis.

After 541 days without a government, the sovereign swore in Prime Minister Elio Di Rupo, sporting one of his iconic red bow-ties, and then his 12 cabinet ministers and six secretaries of state, one by one.

"I swear fidelity to the king, obedience to the constitution and to the laws of the Belgian people," Di Rupo said in French, and then in Dutch and German, the country's three languages, with his right hand raised.

Albert II, who helped steer feuding politicians across Belgium's French-Dutch language divide back to talks, shook hands with each of the members of the new cabinet.

Di Rupo, who will be the country's first French-speaking premier, takes office from a caretaker government headed by Yves Leterme.

Belgium's longstanding finance minister Didier Reynders, 53, swaps portfolios with 47-year-old foreign minister Steven Vanackere in the cabinet.

Women have the portfolios for home affairs, social affairs, middle class and small enterprise, justice and employment.

The ceremony brings relief to Belgium's 10.5 million people exasperated by the endless squabbling between politicians that won Belgium the dubious record of the world's country longest without a government.