At least 130 people were killed, including 10 soldiers, in the deadliest clashes in months between troops and rebels in the restive eastern Democratic Republic of Congo, the government said Monday.
Loud blasts rang out north of the flashpoint city of Goma on Monday afternoon, and up to 1,000 people were seen fleeing towards the city in a cloud of dust, an AFP photographer reported.
"Our forces have inflicted very heavy losses on the M23 fighters, 120 have been killed and 12 captured," said government spokesman Lambert Mende.
Mende said 10 soldiers had also died in the ongoing clashes between the army and the M23 rebel group in the volatile east, an area rich in minerals including gold and coltan, a key component in cell phones and other electronic equipment.
The fierce fighting broke out on Sunday outside Goma, the capital of North Kivu province.
Several Congolese army tanks fired at the positions of the M23 Monday, and mortar fire was also heard.
Mende said the M23, who briefly seized Goma late last year before withdrawing under international pressure, attacked army positions "with the support of Rwandan troops".
"For several weeks the M23 rebels and their Rwandan allies have been reinforcing their positions," he said.
The M23, an armed group launched by Tutsi former soldiers who mutinied from the Congolese army in April 2012, said in a statement that it condemned "in the strongest terms the resumption of war initiated by the Congolese government".
The group, which says it is fighting for the full implementation of a peace deal that incorporated an earlier rebel group into the Congolese army, said it was committed to peace negotiations.
United Nations experts have accused both Rwanda and Uganda of supporting the M23, and US President Barack Obama early this month urged the DR Congo's neighbours "to stop supporting armed groups".
Both countries have denied the charges.
The UN has its largest peacekeeping mission in the world in DR Congo, including a new "intervention brigade" created by the Security Council in March to fight armed groups -- the first offensive unit ever authorised by the UN.
But UN soldiers did not intervene in the recent clashes, Mende said.
Army forces also managed to recapture previously rebel-held positions as the M23 fled, the spokesman said.
Some 2,000 soldiers were reportedly deployed during the fighting but Mende declined to confirm this figure.
The fighting outside Goma comes after a separate rebel attack in the town of Kamango in the northernmost part of the province sent 55,000 people fleeing to neighbouring Uganda, according to the Red Cross.
Kamango was attacked and briefly occupied Thursday by a Ugandan-led rebel group, the Allied Democratic Forces (ADF).
The ADF was formed in the mid-1990s in the Rwenzori mountains in western Uganda, close to the DR Congo border. It has been relatively quiet in recent years, but attacks have increased in the past few weeks, according to a Western military source.
Adding to the tense security situation in the region, a military spokesman in Rwanda said two mortar bombs had been "deliberately" fired into the country from DR Congo on Monday.
He said the mortars, which caused no injuries, were fired in mid-afternoon, and blamed the Congolese army and the UN peacekeeping force on the grounds the bombs were fired from territory they control.
The UN's new intervention brigade of some 3,000 soldiers began arriving in the region in May, heavily armed and with more power to fight renegade forces than ever before.
The troops, drawn in equal numbers from Malawi, South Africa and Tanzania, are joining about 17,000 UN soldiers already deployed in the area with a limited mandate to protect civilians and themselves.
In all, about 30 armed groups are active in the region, where they have lucrative stakes in the illegal mining of diamonds, gold and coltan. These minerals are then exported around the world via neighbouring Burundi, Rwanda and Uganda.