Meles Zenawi (file photo)

Ethiopian Prime Minister Meles Zenawi has dismissed an ultimatum from Somalia's Islamist movement to pull his troops off Somali soil.

Speaking to reporters in Addis Ababa Wednesday, the Ethiopian leader said the Islamists' threat is "nothing new."

On Tuesday, the Islamists threatened a large-scale attack on the Ethiopian troops it says are in Somalia, unless they leave within seven days.

The Islamist security chief, Yusuf Mohamed Siad, asserted there are at least 35,000 Ethiopian troops on Somali territory.

Addis Ababa says it has sent only several hundred military instructors to help the weak Somali transitional government. Ethiopia says it has no plans to withdraw the trainers.

Islamist forces Wednesday said they have captured another town in southern Somalia. The Ufurow settlement was one of the few areas under the government's control in the south.

Somalia's transitional government has little authority outside its base in Baidoa. The Islamist forces have seized increasing amounts of territory since taking control of the capital, Mogadishu, in June.

Diplomats fear the Somali conflict could grow to draw in Ethiopia's rival, Eritrea, which supports the Islamists.

Somalia has been without an effective central authority since 1991.