Abdo Rabbu Mansour Hadi became Yemen's new president Saturday, formally removing autocrat Ali Abdullah Saleh from power, as a car bombing in the south of the country underscored the violence that will be the new leader's greatest challenge. The car loaded with explosives killed at least 26 people and injured dozens when it was driven towards a presidential palace in the southern Yemeni city of Hadramout, far from the capital Sana'a 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 neighbors 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 leader 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 a year of protests and violence and tackle pressing issues such as Yemen's economic problems and bringing those displaced by the crisis back to their homes. “One of the most prominent tasks is the continuation of war against Al-Qaeda as a religious and national duty, and to bring back displaced people to their villages and towns,” Hadi said. “If we don't deal with challenges practically, then chaos will reign.” After his speech, protesters in the southern city of Aden clashed with security forces, injuring four people, medics said. Yemen's neighbors, led by Saudi Arabia, crafted the power transfer, also backed by Washington and a UN Security Council resolution, to ease out Saleh. There are fears that chaos in Yemen could empower the country's branch of Al-Qaeda near major oil shipping routes. Saleh meanwhile returned to Yemen early Saturday after spending about three weeks in the US receiving treatment for injuries he suffered during a June rocket attack on his compound that helped hasten his departure.