The French, US, Rwandan, Ugandan and Kenyan embassies in Democratic Republic of Congo's capital Kinshasa were attacked by protesters, a European diplomatic source said.
The diplomat added that protesters did not enter the French and US embassies.
Meanwhile, the Red Cross voiced alarm over the risk that fighting in the besieged city of Goma could cause samples of Ebola and other pathogens held in a laboratory to escape.
The International Committee of the Red Cross is "very concerned about the situation in the laboratory of the national biomedical research institute, which is facing a risk of power cuts, as well as a question of preserving the samples that may be affected by the clashes", ICRC regional director for Africa Patrick Youssef said.
He warned of "unimaginable consequences if the (samples), including the Ebola virus, that it contains were to spread".
Hospitals in Goma are overwhelmed, treating hundreds of patients with gunshot, mortar and shrapnel wounds while many dead bodies lay in the streets, the UN and and other aid agencies said.
Rwandan-backed M23 rebels marched into Goma yesterday in a major escalation of the three-decade conflict, but continue to face pockets of resistance from the army and their backers.
This morning, heavy small arms fire and mortar fire continued in the streets, where many dead bodies could be seen, said Jens Laerke, spokesperson for the UN humanitarian office, citing reports from staff in the city.
"The humanitarian situation in and around Goma remains extremely worrying," Mr Laerke told a Geneva briefing.
"Hospitals in Goma are reportedly overwhelmed, struggling to manage the influx of wounded people," he added, saying that there were reports of rapes by fighters.
Hundreds of people have been admitted to hospital with gunshot and other wounds, said Adelheid Marschang, the World Health Organization's (WHO) emergency response coordinator for Congo at the same briefing.
"We are hearing reports of health workers being shot at and patients including babies being caught in crossfire," she said.
The Red Cross said that one of its hospitals had received over 100 patients within 24 hours with head wounds and chest trauma from mortar and shrapnel, and that patients were waiting in the corridors for lack of beds.
"Very disturbingly, we have seen a significant increase in the number of severely injured children," said the ICRC's Mr Youssef.
