Democratic Republic of Congo's government and Rwandan-backed M23 rebels traded blame on Friday for several explosions at a rally in the rebel-held eastern city of Bukavu that killed 13 people and wounded scores of others the previous day.

The rebels have been advancing through eastern DR Congo since January, seizing Bukavu and Goma, the biggest city in the region. The fighting has forced about 500,000 people from their homes, worsening an already dire humanitarian crisis, according to the UN.