Somali government soldiers and African Union troops have seized a major Islamist militant training base, a Somali army commander has told the BBC.
Abdikarin Yusuf, deputy army of the Somali military, said al-Shabab fighters withdrew without a fight.
Observers say the capture of Lanta-Buro, 40km (25 miles) west of the capital Mogadishu, is a major setback for the al-Qaeda group.
It still controls much of Somalia but is under pressure on several fronts.
Somalia has been without an effective central government since 1991, and has been wracked by fighting ever since - a situation that has allowed piracy and lawlessness to flourish.
Gen Yusuf, known as "Dhagabadan", told the BBC Somali Service that the offensive launched on Wednesday morning had been successful.
He said the next target was the al-Shabab-held coastal town of Merka.
Lanta-Buro is one of an estimated six training bases al-Shabab has across the country.
Ethiopian troops, pro-government militias and the African Union force - which has US and European funding and was boosted earlier this year to nearly 18,000 - have helped the UN-backed interim government recently expand its control outside Mogadishu.
In the last few months, the militants have lost several key positions, including Afgoye near the capital, Baidoa in central Somalia and the southern town of Afmadow.
However last month, the militants retook their northern base of El Bur - a strategic training camp - after Ethiopian troops withdrew.
Disparate Somali factions have agreed to elect a new president, ending a transitional period and the mandate of the UN-backed interim government, by 20 August.