The Congolese army on Tuesday battled M23 rebels in the country's volatile east, a day after at least 130 people were killed in the deadliest clashes in months.
Army spokesman Colonel Olivier Hamuli said Democratic Republic of Congo forces were gaining ground in the battle close to the North Kivu capital Goma, as they sought to "wipe out M23", a movement launched in April last year by Tutsi defectors from the army.
The United Nations has warned its troops in the flashpoint city of Goma -- which include a recently-deployed offensive brigade -- were on high alert and ready to intervene in case of attack.
Goma -- which was occupied by M23 for 10 days late last year before the rebels withdrew under international pressure -- lies in a region rich in minerals including gold and coltan, a key component in cell phones and other electronic equipment.
The commander of M23 operations in the area, Colonel Youssouf Boneza, told AFP by telephone that "M23 is holding its positions in spite of heavy shelling".
An AFP photographer in Kanyarucinya, a town 15 kilometres (nine miles) from Goma, reported a heavy army presence, but no clashes. However, he heard two rocket explosions to the north.
Both the army spokesman and residents in the region reported a lull in fighting and heavy weapons fire by late Tuesday afternoon.
Each side has accused the other of starting the fighting on Sunday, and the government has revived an allegation that M23 is receiving support from Rwandan troops in the heaviest clashes in months.
"For several weeks the M23 rebels and their Rwandan allies have been reinforcing their positions," said government spokesman Lambert Mende on Monday. Neighbouring Rwanda strongly reject all charges of support for M23.
"Our forces have inflicted very heavy losses on the M23 fighters, 120 have been killed and 12 captured," for the loss of 10 government soldiers, Mende said.
Casualty figures could not be independently verified. The army was keeping journalists away from the battle zone and M23 has so far issued no toll.
In March, the UN Security Council decided to boost the UN mission in DR Congo (MONUSCO) with an offensive brigade of 3,000 men who were given an unprecedented mandate to neutralise and disarm rebel groups operating in eastern DR Congo.
MONUSCO "has put its troops on high alert and stands ready to take any necessary measures, including the use of lethal force, to protect civilians," UN spokesman Martin Nesirky announced in New York.
"The mission says that any attempt by the M23 to advance toward Goma will be considered a direct threat to civilians," he said, adding that the rebels had reinforced their positions around the city with heavy artillery and an armoured car.
About two-thirds of the new force, which comprises troops from Malawi, South Africa and Tanzania, have arrived. It is expected to be active within the next few weeks.
Late Monday, Rwanda's army spokesman, General Joseph Nzabamwita, accused the Congolese army and UN forces of shelling two Rwandan border villages in what he called "a provocative and deliberate act by FARDC and MONUSCO".
Neither the Congolese army nor the UN mission were available to comment on the allegation.