Somalia Prime Minister Ali Mohamed Gedi said his troops, supported by Ethiopian tanks and MiG fighter jets, were going after three al Qaeda terror suspects wanted in the 1998 bombings of U.S. embassies in east Africa that killed more than 250 people.
He said Islamic militants in Kismayo, Somalia's third-largest city, were sheltering accused bombers Fazul Abdullah Mohammed, Saleh Ali Saleh Nabhan and Abu Taha al-Sudani.
The fighting broke out in Helashid, 18 kilometers (11 miles) northwest of Jilib, the gateway to the Islamic group's coastal stronghold of Kismayo, where an estimated 3,000 hardcore Islamic fighters were preparing for a bloody showdown.
"I can hear artillery and heavy weapons being fired outside of town," said Abdi Malik, a charity worker in Jilib, told The Associated Press by telephone.
Both sides were fighting in thick mango forests, which was providing cover for the Islamic militia from tanks and aircraft, villager Mohamed Deq told the AP.
"They are both firing mortars and artillery shells," he said. "It is heavy, and we can hear a lot of machine gun fire hitting the buildings."
Ethiopian MiG fighter jets were also buzzing Kismayo, an AP reporter said.
Islamic leaders vowed to make a stand against Ethiopia, which has one of the largest armies in Africa, or begin an Iraq-style guerrilla war.
"My fighters will defeat the Ethiopians forces," Sheik Ahmed Mohamed Islan, the head of the Islamic movement in the Kismayo region, told the AP.
"Even if we are defeated, we will start an insurgency. We will kill every Somali that supports the government and Ethiopians."
Jilib resident Mohamed Suldan Ali said the Islamic forces had littered the approach to the town with remote-controlled land mines. Another resident said the fighters had destroyed three bridges on the approaches to the town.
Somalia's interim government and its Ethiopian allies have long accused Islamic militias of harboring al Qaeda, and the U.S. government has said the 1998 bombers have become leaders in the Islamic movement in Africa.
"We would like to capture or kill these guys at any cost," Prime Minister Gedi told the AP. "They are the root of the problem."
Up to 2,000 people, carrying what they could, streamed out of the southern Somali town of Jilib. "I don't know where to go. We are terrified because we can hear the fighting," said Howo Nor, a mother of three children who lives in Jilib.
Many were headed for the Kenyan border.
In the past 10 days, the Islamic group has been forced from the capital, Mogadishu, and other key towns in the face of attacks led by Ethiopia, the region's greatest military power.
Gedi said he spoke Sunday to the U.S. ambassador in Kenya, Michael Ranneberger, about sealing the Kenyan border with Somalia to prevent the three terror suspects from escaping.
"If we capture them alive we will hand them over to the United States," Gedi said. "We know they are in Kismayo."
The U.S. government has a counterterrorism task force based in neighboring Djibouti and has been training Kenyan and Ethiopian forces to protect their borders. The U.S. Navy's Fifth Fleet also has a maritime task force patrolling international waters off the Somali coast. It will prevent terrorists from launching an "attack or to transport personnel, weapons or other material," Commander Kevin Aandahl, spokesman for the Fifth Fleet, told the AP.
Islamic movement leaders deny having any links to Osama bin Laden's al Qaeda terror network.
But in a recorded message posted on the Internet on Saturday, deputy al Qaeda leader Ayman al-Zawahri called on Somalia's Muslims and other Muslims worldwide to continue the fight against "infidels and crusaders."
Gedi accused al-Zawahri of trying to destabilize Somalia and its neighbors.
The military advance marked a stunning turnaround for Somalia's government, which just weeks ago could barely control one town — its base of Baidoa — while the Council of Islamic Courts controlled the capital and much of southern Somalia.
The Council of Islamic Courts, the umbrella group for the Islamic movement that ruled Mogadishu for six months, has pledged to continue its fight, despite military losses.
The group wants to transform Somalia into a strict Islamic state.
Islamic officials claimed they still had fighters in the capital and were ready for warfare. Late Saturday, an unexplained blast in the capital left one woman dead and two others wounded and stirred fears of a guerrilla war.