Somali forces killed about 40 al-Shabaab fighters in the Middle Shabelle region, the government said on Thursday, the latest clashes in a months-long offensive that aims to weaken the grip of the Islamist militant group.

Al-Shabaab, an al-Qaeda franchise that is seeking impose its interpretation of Islamic law across the country, frequently stages deadly attacks in the capital Mogadishu and elsewhere.

"The security forces and our international allies killed around 40 Al-Shabaab fighters and wounded several others," Somalia's information ministry said in a statement.

The ministry described it as a planned operation in a forest near the village of Ali Foldhere in Middle Shabelle on Wednesday night, but Al-Shabaab and one clan fighter said the fighting arose from an attack by the militants.

The government, supported by clan militias and African Union troops, says it has killed more than 600 members of Al-Shabaab and recaptured 68 settlements over the last three months, as part of concerted efforts to end the militants' control over large portions of the Horn of Africa country.

(With input from Reuters)