A United States drone strike has killed more than 150 Al-Shabaab militants in Somalia, the Pentagon says.

The US attack was executed on March 5, a day before more than 2,000 weapons were seized on a Somalia-bound boat by the Australian Navy on Sunday, two blows likely to cripple the terror militia.

The Australian Navy suspected the weapons were for arming the Al-Shabaab terror group.

Pentagon spokesman Captain Jeff Davis said the strike hit Raso training camp where a "large-scale" attack was being planned against US and Amisom troops in the country.

"We know they were going to be departing the camp and they posed an imminent threat to US and [African Union] forces," Captain Davis said.

"Initial assessments are that more than 150 terrorist fighters were eliminated," he added.

Mr Davis said the strike, on Saturday, targeted a camp about 120 miles (195km) north of the capital, Mogadishu.

The camp had been under surveillance for some time ahead of the drone strike, according to Mr Davis.

"There was a sense that the operational phase was about to happen," he said.

He said the group had neared the completion of specialist training to conduct "offensive operations", but did not give any details about the alleged plot.

AUSTRALIAN NAVY

More than 2,000 weapons including assault rifles, rocket launchers and machine guns were found hidden under fishing nets in a Somalia-bound boat, Australian Navy officials said Monday.

The HMAS Darwin navy ship seized the weapons from the vessel during normal patrol of the Middle East-Eastern Africa coast waters.

Sunday’s recovery of the weapons could signal a continual but clandestine attempt by the Shabaab to keep their supply of arms despite a global operation against the terror group.

On Monday, Australia’s Vice Admiral David Johnston who is also the Chief of Joint Operations for the multi-nation patrol operation called Combined Maritime Forces, said the seizure of weapons could be significant even though there was no revelation of their origin.

KDF OPERATIONS

In February this year, the Kenya Defence Forces raided Al-Shabaab training camps in two attacks, killing 53 terrorists including the group's deputy leader in the first attack, and killing 20 other terrorists in the second attack at the Sidimo camp.

The first attack killed Al-Shabaab's deputy emir, the second in command and heat of its intelligence wing, the Amniyaat, Mahad Karate, also known as Abdirahim Mohamed Warsame.

The raid happened on February 8, but details of the attack at an Al-Shabaab base between Buale and Sukow were delayed to allow for forensic confirmation to ascertain its leader was among those killed.

The second attack was conducted on February 18. KDF ground troops raided an Al-Shabaab camp in Sidimo, killing 20 terrorists, among them explosives expert Maalim Sheriff.

They found 16 AK-47 rifles, six improvised explosives, two pistols, eight rocket propelled grenades and assorted ammunition.

Sustained operations have been ongoing since the attack at a KDF camp in El-Adde.

“Karate had gone to the camp to preside over the passing out of an estimated 80 Alamnyat recruits who had completed their training and were due for deployment to carry out terrorist attacks. It is confirmed that 42 recruits were killed and others sustained injuries,” said military spokesman David Obonyo.

Karate is believed to have played a key role in the El-Adde attack

Al-Shabab, an affiliate of Al-Qaeda, was pushed out of Mogadishu by African Union peacekeeping forces in 2011 but has continued to launch frequent attacks in its bid to overthrow the Western-backed government.

The group has said it carried out a string of recent attacks including a twin bombing at a busy restaurant in the Somali city of Baidoa last month.