Somalia's Islamist militant group al-Shabaab has executed three men it accused of spying for the United States Central Intelligence Agency (CIA) and other intelligence agencies, the pro-al-Shabaab website Somali Memo reports.

The three were killed in front of a large crowd in southwestern town of Yaq-Barawe.

Abdullahi Damey Mohamed Nur, 36, was "found guilty of spying for the CIA, and earned a salary of $200 [£158] a month", the website said.

An al-Shabaab judge said Mohamed admitted helping the US target the group's officials using drone strikes.

The judge also said Mohamed Iman Hassan, 42, was executed for spying for Kenya and earned a salary of $150.

Mohamed Sharif Ali, 21, was accused of helping Jubbaland regional administration to collect information on al-Shabaab.

The al-Qaeda-linked group arrests people who do not agree with its ideology and accuses them of spying and are later killed.

In 2011, Muslim cleric Ahmed Ali Hussein was chained and shot dead after being accused of being a CIA spy and belonging to a sect opposed to the group.

The group is fighting to overthrow the UN-backed Somalia government and form its own version of an Islamic state.