The Democratic Republic of Congo's army has launched an offensive against rebel leader Laurent Nkunda, using helicopter gunships and heavy artillery.
It is the start of a long-expected offensive against Gen Nkunda
Fighting is taking place in Mushake, a rebel town 40km north-west of Goma, a day after the army lost one battle.
There are reports that the army has retaken some villages in the east that were captured by Gen Nkunda's men.
A BBC correspondent in the region says there were jubilant soldiers on the road between Sake and Goma.
Government forces have repeatedly threatened Gen Nkunda with force unless he relinquishes his control over areas close to the Rwandan border.
Gen Nkunda claims he is defending his own Tutsi community against Rwandan Hutu rebels responsible for the Rwandan genocide in 1994, who have been roaming the east of DR Congo ever since.
The BBC's Arnaud Zajtman in the east of DR Congo says the attack is the start of a long-anticipated offensive.
Mushake looks over a key road that links the regional capital, Goma, with valuable tin mines and rich farming land further west, he says.
The small hillside town is a stronghold of the rebels and its buzzing market centre is inhabited mainly by Tutsi cattle farmers.
It is being attacked by ground troops using heavy artillery supported by two attack helicopters.
A military spokesman for the UN mission in DR Congo said UN peacekeepers are bringing logistic support to the government forces, but are not engaged in any fighting.
The attack comes a day after the rebels captured the town of Nyanzale, about 100km further north.
The rebels forced the government soldiers to pull out and took control of their military base there.
Witnesses said over 40,000 civilians fled as a result.
There were no reports of civilian casualties but medical sources told the AFP news agency that several wounded government soldiers were in nearby hospitals.
The elected Congolese government has made a commitment to flush out the Rwandan Hutu rebels, and says Mr Nkunda and his 6,000-8,000 men should also lay down their arms.
Some 15,000 UN peacekeepers are in DR Congo to secure peace after a five-year conflict officially ended in 2002.