The United States has launched an air strike targeting a senior leader of Somalia's al-Shabab group, the Pentagon has said.

The US Defence Department did not identify the leader or say whether the strike was successful.

"The strike took place in the vicinity of Saacow, Somalia," spokesman Mark Wright said in a statement on Monday.

"At this time, we do not assess there to be any civilian or bystander casualties.

"We are assessing the results of the operation and will provide additional information, when appropriate, as details become available."

Al-Shabab fighters are fighting to overthrow the Somali government, regularly launching attacks against state targets and in neighbouring countries that contribute to an African Union force operating in the country.

Source: Agencies