Ethiopia has dismissed a declaration of war by an official of a radical rebel group in neighboring Somalia, saying it appears to be an empty threat.  But, African leaders at a summit in Libya are seriously concerned by reports that foreign Islamic fighters are pouring into Somalia to join the insurgents.

Ethiopia's Communications Minister Bereket Simon scoffed at word a member of the al-Shabab rebel group in the Somali town of Kismayo had threatened to invade Ethiopia. 

The militant leader's comments were broadcast on an al-Shabab radio station in Kismayo, a port along Somalia's southern coast, about 200 kilometers from the Kenyan border. 

Kenya appears to be taking the al-Shabab threat more seriously.  Kenyan troops have been on high alert along the border for some time.

Ethiopian minister Bereket told reporters the rebels have their hands full trying to capture the Somali capital, Mogadishu, and pose no threat to Ethiopia at this time.

"This declaration of war is coming from Kismayo, not from Mogadishu," said Bereket Simon. "I think al-Shabab has a formidable task of conquering Mogadishu fully first, before they drag their feet to Ethiopia, so for the time being we know we can comfortably say this is some form of grandstanding by al-Shabab, but we are closely following the situation."

Bereket again categorically rejected reports Ethiopian troops are moving back into Somalia.  Ethiopia invaded its Horn of Africa neighbor in 2006 to restore the transitional government to power in Mogadishu, but withdrew earlier this year.

Bereket said there is no plan to go back.

"We are within our borders," he said. "We are continuously monitoring and following the situation.  So for monitoring purposes, within the vicinity of our boundaries, we might move here and there, nonetheless, we have no operational army in Somalia, and we will not have."

Bereket says Ethiopia, as leader of the six-nation East Africa regional group known as IGAD, is pushing leaders attending the African Union summit in Libya to radically upgrade the AMISOM peacekeeping mission to make it a fighting force that could counter the al-Shabab threat.

"We have asked the African Union to beef up capacity of AMISOM, because with that capacity beefed up, possibility of stabilizing the situation will be increased," said Bereket. "Secondly, we also asked for change of mandate because that would entail additional capacity in many respects."

IGAD, meeting on the A.U. summit sidelines, blamed the recent surge of violence in Mogadishu on the arrival of as many as 2,000 foreign fighters. The group also reiterated its call for the United Nations to impose sanctions on another Horn of Africa neighbor, Eritrea, for fueling the conflict.

AU Commission Chairman Jean Ping is urging summit leaders to act quickly.  He was quoted as saying the continental body is the only entity capable of intervening to stabilize Somalia.

The United States underscored the urgency of the threat last week when it announced it had sent a $10-million shipment of weapons and ammunition to help Somalia's government defend itself.

The United Nations estimates 250 civilians have been killed since fighting around Mogadishu intensified two months ago. The violence also triggered a fresh exodus of refugees to Kenya and Ethiopia.  Officials in Addis Ababa say the recent influx of refugees has raised the city's Somali population to 120,000.