Abd-Rabbu Mansour Hadi took the constitutional oath to become Yemen's new president on Saturday, formally removing Ali Abdullah Saleh from power after a year of protests paralysed the Arabian Peninsula nation.
In a reminder of the violence that has longed plagued Yemen, a car loaded with explosives killed at least 26 people and injured dozens when it was driven towards a presidential palace in the southern city of Hadramout, far from the capital Sanaa where Hadi was sworn in.
A former army general, Hadi stood as the sole candidate to replace Saleh in a power transfer deal brokered by Gulf neighbours and backed by Western powers. He was elected after more than 60 percent of eligible voters took part in an election this week.
Saleh's departure makes him the fourth Arab autocrat to be removed from power in more than a year of mass uprisings that have redrawn the political map of the Middle East.
Hadi said in a speech that Yemen must draw a line under the crisis and tackle pressing issues such as Yemen's economic problems and bringing those displaced by the crisis back to their homes.
I stand here in a historic moment... I look to the Yemeni people and give them thanks. The crisis reached every city and village and house, but Yemen will continue to go forward, Hadi said. If we don't deal with challenges practically, then chaos will reign.
After his speech, protestors in the southern city of Aden clashed with security forces, injuring four people, medics said.
Yemen's richer neighbours, led by Saudi Arabia, crafted the power transfer, also backed by Washington and a U.N. Security Council resolution, to ease out Saleh, who had ruled Yemen for 33 years.
One of the poorest countries in the Middle East, Yemen had already been fractured before the revolt against Saleh's rule, with separatists in the south, Shi'ite rebels in the north and an active wing of al Qaeda.
There are fears that chaos in Yemen could empower the country's branch of al Qaeda near major oil shipping routes.
Hadi now is tasked with overseeing a proposed two-year political transition that envisions parliamentary elections, a new constitution and restructuring of the military in which Saleh's son and nephew still hold power.
Hadi made a point to single out al Qaeda as a top priority for his new administration: Continuing the war against al Qaeda is a national and religious duty.
The international community described the oath as a key step forward.
Yemenis want an end to the crisis, and to turn a new page. Now it's time to rebuild, for consensus and concord... and to bring people into an inclusive political process, said Jamal Benomar, U.N. envoy to Yemen.
The U.S. ambassador to Yemen, Gerald Feierstein, said: We are seeing the beginning of a process that I believe will deliver great results over the next two years.
Hadi's inauguration ceremony is scheduled for Monday, which Saleh is to attend. Saleh returned to Yemen on Friday after seeking treatment in the United States for injuries suffered in a assassination attempt last year.
A high election turnout was deemed crucial to Hadi's legitimacy, but the vote was rejected in advance in wide swathes of the country, notably the south, where secessionists urged a boycott.
Some 42 percent of Yemen's population of 23 million live on less than $2 per day in a land where tribal loyalties remain central to society.
If Abd-Rabbu Hadi doesn't rein in the mashayikh (tribal notables) then we'd be better off with Ali Abdullah Saleh, said Amin al-Sharaby, 24, after gunmen loyal to a tribal leader scuffled with bystanders outside door of parliament, and beat a man with the butts of their rifles.
(Additional reporting by Nour Merza in Dubai and Mohammed Mukhashaf in Aden; Writing by Reed Stevenson; Editing by Rosalind Russell)