Somali government and African Union troops have seized a critical port town from al-Shabab, dealing another blow to the Islamist militant group.

The pro-government forces seized the town of Merca on Monday, according to a tweet posted by the African Union Mission in Somalia .

Residents confirmed to VOA that al-Shabab fighters have fled the town.

The port is located about 100 kilometers south of the capital Mogadishu.

Merca was critical to al-Shabab because it offers sea access and is located along a route to Port Kismayo, the largest town still under the militant group's control.

According to witnesses, pro-government troops engaged in small-scale fighting with the militants Monday in the nearby town of Shalambood, prompting militants in Merca to flee.

Residents said Somali and AU troops met no resistance when they entered the port town on Monday afternoon.

Al-Shabab has lost a lot of territory in southern and central Somalia since international forces launched three separate offensives against the group last year.

Ethiopian, Kenyan and Somali government troops backed by the AU are fighting to push out al-Shabab.

The group has been fighting to overthrow Somalia's government and impose a strict form of Sharia, or Islamic law.