Colonel Olivier Hamuli, spokesman for the Congolese army (FARDC) in North Kivu province, said that M23 forces had attacked FARDC positions in the same zone as yesterday, when clashes broke out 12 kilometres north of Goma, the provincial capital.
"We're keeping a fierce response in store for them," Hamuli added, while declining to give any toll from the fighting, which was the first involving the M23 army mutineers since December.
A Western military expert said M23 was fighting with mortars and armoured vehicles captured from government troops last November. The FARDC was using multiple-barrel cannons, he added.
No spokesmen for the rebel force could be reached, but in a statement sent overnight to AFP, M23 denounced the "military option" taken by the government and reaffirmed the movement's commitment to peace talks in the Ugandan capital Kampala.
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Ban today said during a visit to Mozambique that the flare-up in the DRC meant that the deployment of a UN military taskforce with a tough mandate to attack rebel forces should be speeded up.
"Considering what has happened I think we must expedite the deployment so they will be fully responsible as soon as possible," Ban said in the wake of the arrival of the first batch of troops last week.
M23 rebels in April vowed to retaliate if attacked by UN troops after the UN Security Council approved the creation of the 2,500-strong force.