The authorities in Congo Brazzaville say they've launched an offensive south of the capital, Brazzaville, on the rebel militia of the former prime minister Bernard Kolelas, who are trying to topple the government of Denis Sassou Nguesso.

The government forces repelled an attempt by the militia, known as Ninjas, to take the capital last month.

The authorities say the Ninja's are holding residents hostage in villages south of the capital but the rebels have denied this.

One resident contacted by the Associated Press News Agency said about two-thousand women and children were being forced to stay in their homes in two towns near the southern outskirts of Brazzaville.