Somalia?s pro-government troops seized a key southern town from their Islamist rivals yesterday in the closest battle yet to the religious movement?s Mogadishu stronghold, witnesses said.

`?The government has taken over Jowhar. I can see government troops on top of armoured vehicles chasing Islamists troops... heading towards Mogadishu,? resident Mahamud Ismail said from the town 90 km (56 miles) north of the Islamist-held capital.

Residents left their houses to cheer pro-government troops, backed by Ethiopian tanks, which pursued the Islamists as sporadic gunfire echoed in the air, witnesses said.

Government spokesman Abdirahman Dinari said his forces were advancing on Balad, a town between Jowhar and the capital.

?We will not go into Mogadishu today,? he said. The capture of Jowhar came hours after Ethiopia, defending the Somali interim government, said it was halfway to crushing the Islamists, heightening fears its next step would be to use airstrikes and ground troops to seize the capital.

The retreating Islamists appeared to be heeding a call by their senior leader Sheikh Sharif Ahmed for forces to gather in Mogadishu to prepare for a long war against old foe Ethiopia.

?Most of our troops should converge in and around our bases in Mogadishu and should prepare for a very long war against our enemies,? he told reporters late on Tuesday.

A week of mortar duels between Islamists and the Ethiopian-backed secular government has spiralled into open war that threatens to engulf the Horn of Africa.