The US military says it has killed three al-Shabaab extremists with an airstrike in central Somalia as it continues to attack a new base of operations for the al-Qaeda-linked fighters.

The US Africa Command statement says Tuesday's airstrike was carried out "in the vicinity of Quy Cad near Debatscile" in the Mudug region.

The US last week reported several airstrikes in Mudug killed 50 al-Shabab extremists. The group recently relocated to the region as a key training and planning base after the US and allies increased pressure and surveillance further south.

The US military has carried out at least 36 airstrikes this year against al-Shabaab, one of Africa's deadliest Islamic extremist groups, which continues to stage deadly attacks in the capital, Mogadishu, and other cities.