Somalia's Islamic extremist rebels, al-Shabaab, named Abu Ubeid Ahmed Omar to be their new leader following the killing of previous leader by a U.S. airstrike, said a commander of the group.

The Somali militants unanimously selected Omar on Saturday at a meeting in an undisclosed location in Somalia, said rebel commander Abu Mohammed. Omar is believed to be an assumed name, and the new leader's real name is not known.

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

The Somali group had to appoint a new leader following the death of Ahmed Abdi Godane who was killed by a U.S. airstrike Monday. The attack took place 105 miles south of Mogadishu, where al-Shabaab trains its fighters.

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-Qaida-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 the deadly Westgate Mall attack in Nairobi, Kenya that left 67 people dead one year ago.

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

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 the al-Qaida-linked group 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 Oct 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.