Kenyan military officials say their navy has sunk another boat carrying suspected al-Shabab militants.

A Navy spokesman says Kenyan forces fired on the boat in the area Ras Kamboni on Friday, after the vessel refused to stop for identification as it sped toward Kenyan waters.

Kenya has not confirmed the number of casualties.

Earlier this week, Kenyan Major Emmanuel Chirchir posted a video link on his Twitter page that he says shows the Kenyan Navy sinking a vessel with 18 al-Shabab fighters.

He said all the militants were killed in the attack. The video's authenticity could not be confirmed.

Chirchir said Kenyan troops are poised to sweep across 10 towns in southern Somalia in pursuit of al-Shabab. The militant group has summoned reinforcements from other parts of the country.

The Kenyan military launched an offensive in Somali three weeks ago aimed at militants. The government has accused al-Shabab militants of crossing into Kenyan territory from Somalia and kidnapping several foreigners.

Al-Shabab has been fighting since 2008 to topple the Somali government. The group was recently left the capital, Mogadishu, but still controls large sections of southern and central Somalia.