Yemen’s defense minister escaped a suicide bomb attack on his convoy Tuesday in the volatile southern city of Aden, an assault that government officials blamed on al-Qaeda.

It was the second attempt to kill Defense Minister Mohammed Nasser Ahmed in less than a month, underscoring the tense environment in Yemen’s south, where al-Qaeda-linked militants have taken control of large swaths of territory this year.

A suicide bomber driving a car detonated explosives alongside the minister’s convoy on a coastal highway in Aden. The government said in a statement that several members of the minister’s security detail were injured but that he was unharmed. No group asserted responsibility, but the government blamed “al-Qaeda terrorists.”

Late last month, Ahmed’s vehicle struck a land mine in Abyan province, also in the south, killing two of his bodyguards.

Tuesday’s attack comes five days after President Ali Abdullah Saleh suddenly returned to Yemen after nearly four months in Saudi Arabia, where he was treated for injuries suffered in a June attack on his presidential compound. Many Yemenis fear that his return will stoke more violence in this nation, the Middle East’s poorest, which has been gripped by a populist uprising for eight months.

Although Aden has not experienced the sort of urban warfare that has taken place in the capital, Sanaa, and other cities, it has nevertheless become a focal point of tension. Al-Qaeda militants have taken over areas northeast of Aden in Abyan province, including the provincial capital, Zinjibar, and are engaged in fierce battles with government forces. Suicide bombings and attacks against soldiers have increased in recent months in Aden, and thousands have been displaced by the fighting in Abyan.

On Wednesday, Yemeni tribesmen shot down a warplane and captured its pilot in an area northeast of Sanaa where the country’s air force was bombarding pro-opposition tribesmen, wire services reported, citing military and tribal sources.

The Obama administration and its allies are concerned about the turmoil in the south, which has long provided a haven for al-Qaeda’s Yemen branch. Al-Qaeda in the Arabian Peninsula has tried to attack in the United States twice since December 2009, and U.S. officials have publicly declared it the most dangerous al-Qaeda wing. Aden is also nestled along major shipping routes, where 3 million barrels of oil pass daily, creating potential targets for the network if it deepens its foothold.

The violence in Sanaa, which last week and over the weekend left more than 150 dead, has subsided, but tensions remain. On Tuesday, thousands of people took to the streets, demanding that Saleh step down.