Somalia's Islamic extremist rebels, al-Shabaab, named a new leader Saturday after confirming the killing of their previous leader by a U.S. airstrike, a commander of the group said.

The Somali militants unanimously selected Ahmad Umar, also known as Abu Ubaidah, at a meeting in an undisclosed location in Somalia, said rebel commander Abu Mohammed.

Al-Shabaab also stated that it remains aligned with al-Qaeda, according to the Site Intelligence Group, that monitors statements by Islamic militant groups.

There had been speculation by analylists that al-Shabaab would be shaken by a power struggle over the selection of a new leader and that perhaps the Somali rebels would change their alliance and become allied to the Islamic State group operating in Syria and Iraq.

Al-Shabaab is believed to have thousands of fighters in its ranks, fighting to impose Sharia law on Somalia. (Farah Abdi Warsameh/File/Associated Press) The Somali group had to appoint a new leader following the death of Ahmed Abdi Godane who was killed with two other officials by a U.S. airstrike Monday. The attack took place 170 kilometres south of Mogadishu, where al-Shabaab trains its fighters.

"Avenging the death of our scholars and leaders is a binding obligation on our shoulders that we will never relinquish nor forget no matter how long it takes," said the al-Shabaab statement, according to SITE.

U.S. President Barack Obama confirmed Friday that Godane was killed by the U.S. airstrike. The U.S. State Department declared al-Shabaab a terrorist organization in February 2008.

Godane was also known as Mukhtar Abu Zubeyr and was the spiritual leader of the al-Qaeda-linked group. The U.S. had offered a reward of up to $7 million for information leading to his arrest. Godane had publicly claimed al-Shabaab was responsible for last year's deadly Westgate Mall attack in Nairobi, Kenya, that left 67 people dead one year ago.

Intelligence says retaliation attacks planned

Somalia's government said Friday night that it has credible intelligence al-Shabaab is planning attacks in retaliation for Godane's death.

U.S. Navy Rear Admiral John Kirby confirmed Monday that U.S. forces had targeted al-Shabaab militants in Somalia, just one day after the group claimed responsibility for an attack on a military prison. (Alex Wong/Getty Images) In a televised speech, Gen. Khalif Ahmed Ereg, Somalia's national security minister, said possible targets include medical and educational institutions. Ereg said the government is vigilant and its armed forces are prepared to prevent such attacks.

The killing of Godane was a "delightful victory," said Ereg. He called on militants still fighting for al-Shabaab to surrender to get a "brighter" life from the government.

Kenyan President Uhuru Kenyatta Saturday thanked the U.S. for killing Godane, saying his death provides "a small measure of closure" for victims of the Westgate Mall attack. Kenyatta's nephew and his fiance died in that attack, a year ago this month.

Godane, who used a number of other aliases, led the planning and was responsible for the perpetration of the attack on Westgate, Kenyatta said.

"We owe the United States, and its soldiers, our heartfelt thanks for bringing an end to Godane's career of death and destruction; and finally allowing us to begin our healing," he said.

"His death is a stark reminder that those who live by the sword shall perish by the sword," Kenyatta said.

Al-Shabaab has vowed to revenge the presence of Kenyan troops in Somalia. Kenyan troops went into Somalia in October 2011 to fight al-Shabaab, which is blamed for cross-border attacks and kidnappings of westerners on Kenyan soil.

Kenya later became part of the African Union force that is bolstering Somalia's weak U.N.-backed government against al-Shabaab's insurgency.

The U.S. State Department declared al-Shabaab a terrorist organization in February 2008.