Islamic militia and secular fighters pounded each other with heavy artillery and mortar fire Saturday as the death toll rose to 142 in seven days of fighting for control of a neighborhood north of the capital.

Residents worried that fighting may spread to other areas after rival militias deployed near the road linking Mogadishu to southern Somalia — the only route currently accessible to civilians.

At least seven people were killed and 14 injured early Saturday as battles continued between fighters from the Islamic Court Union and the Alliance for the Restoration of Peace and Counterterrorism. Thousands of residents have fled their homes to escape the violence, leaving the Sii-Sii neighborhood largely deserted other than the militants.

Militia loyal to the Islamic Court Union, a grouping of radical Islamic leaders banded together in a self-appointed court system, have been fighting since Sunday to capture a strategic road through northern Mogadishu from the alliance.

The secular militia deployed fighters at checkpoints on the five main roads linking Mogadishu with the rest of the country to prevent the Islamist combatants from receiving reinforcements, spokesman Hussein Gutale Ragheh said.

Residents who ventured into the battle zone to check on their abandoned homes said fighting eased somewhat on Saturday, apparently because combatants were tired after days of heavy fighting.

The U.S. Embassy in Nairobi issued a news release late Friday calling "upon all parties to cease combat immediately."

"We urge all parties to return to the path of dialogue and reconciliation and work within the framework of the transitional federal institutions," the release said, referring to a new government attempting to establish control of the country.

Past violence in Somalia has been largely along clan lines and economically motivated. But the battle that broke out a week ago appears to be ideological — over whether Somalia should be governed by Islamic law — fueling what Mogadishu residents described as the worst fighting in more than a decade of lawlessness.

Most of the dead have been civilians caught in the crossfire. Fighters began looting some of the homes in between intense fire fights throughout Friday, witnesses said.

Hospitals are overwhelmed by casualties — with doctors saying 142 people have been killed and more than 280 people injured since last Sunday. The facilities were running out of medicines, said Abdi Ibrahim Jiya of the Medina Hospital.

Clan elders appeared to have abandoned efforts to negotiate a cease-fire, and so far neither side has gained an upper hand.

The alliance accuses the Islamic group of having ties to al-Qaida, while the court union says the warlords are puppets of the United States.

The courts are popular in Mogadishu because in recent years they have provided the only form of order in the city, although in the past they have always been divided along clan lines. They also are considered by many to be fighting for Somalia, not an outside force.

Islamic fundamentalists have portrayed themselves as an alternative capable of bringing order and peace to a country that has had no effective central government since 1991. They have built up their forces as part of a campaign to install an Islamic government in Somalia — something opposed by warlords and a new interim government that has been unable to assert much authority because of infighting and insecurity.

The U.N.-backed transitional government has tried to assert control from Baidoa, 150 miles west of Mogadishu, because the capital is considered unsafe. Some of the warlords behind the alliance are members of the transitional parliament, although they are fighting the Islamic group on their own.

This latest fighting may only be the beginning. Other clan militias with loose loyalties to both sides have not joined in the fighting yet, but they continue to man defenses in the neighborhoods they control, and tensions are rising.