(Changes dateline, adds army quotes, death toll, details)

By Joe Bavier

SAKE, Congo, Dec 3 (Reuters) - Congo's army attacked a stronghold of renegade Tutsi General Laurent Nkunda on Monday, a day after his men took a strategic town from the government and forced out thousands of civilians, U.N. and army officials said.

The army began shelling rebel positions around Mushake, 40 km (25 miles) west of North Kivu's provincial capital Goma, early on Monday after reinforcing its positions there overnight.

"We expect to take Mushake shortly. We are looking at how we can take it as quickly as possible. That's our first objective," General Vainqueur Mayala, the top army commander in North Kivu, told journalists at his mobile headquarters outside Sake, 20 km (12 miles) west of Goma.

The sounds of army artillery and heavy machinegun fire were heard throughout the day around Sake. During early morning fighting, Nkunda's insurgents were driven from hilltop positions which they had held for months overlooking the town.

Army attack helicopters bombarded targets around Sake and Mushake, and U.N. helicopters took to the air, said Major Vivek Goyal, acting military spokesman in North Kivu for Democratic Republic of Congo's U.N. peacekeeping force (MONUC).

"We are engaged in a show of force operation in the area, but our attack helicopters have not fired," Goyal said.

Eight government soldiers were wounded in the clashes, and one was killed, Mayala said, adding that the bodies of a number of Nkunda loyalists were abandoned around Sake.

Sake, on the road to Mushake, has twice fallen to Nkunda in a year and serves as a staging point for the army. MONUC has said any rebel attempt to take the town would be met with force.

Nkunda's fighters attacked government positions on Sunday, routing army forces in the town of Kikuku before sweeping into Nyanzale, around 100 km (64 miles) north of Goma, and seizing an army base there, military and civilian sources said.

"There was heavy fighting throughout the afternoon ... Nkunda took Kikuku and Nyanzale, and the population has all fled. It's empty," said a source, who asked not to be named.

Humanitarian officials said thousands were on the move.

OFFENSIVE EXPECTED

Mushake has been an important base for Nkunda's 4,000-strong rebel force since fighting broke out in late August. The rebels abandoned a Rwandan-brokered peace deal and quit special mixed army brigades formed in early 2007 to stem violence in North Kivu following Congo's 1998-2003 war.

Nkunda first led two army brigades into the bush in 2004 saying he would protect eastern Congo's Tutsi minority.

Mayala refused to say whether the attack was the start of a broader offensive against the general.

Nkunda's spokesman Rene Abandi said: "This is the beginning of their offensive ... We are ready to defend ourselves."

In October, President Joseph Kabila gave a green light to the army to plan an offensive to forcibly disarm Nkunda's men after they missed deadlines to disarm and rejoin the army.

MONUC said last month it was preparing to help the army force Nkunda and his men to surrender. (Edited by Alistair Thomson and Elizabeth Piper)

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