Twenty-five soldiers with the Democratic Republic of Congo's army have been sentenced to death for fleeing battles against the notorious M23 rebels in the conflict-hit east of the country.

The soldiers were also convicted of theft by a military tribunal as they stole goods from shops in a nearby village after abandoning their positions, an army spokesman said.

Four of the soldiers' wives were acquitted by the military court of receiving goods looted by their husbands.

In March, the government lifted a moratorium, in place for more than 20 years, on the death penalty being carried out after the justice minister cited the need to remove "traitors" from the army.

A lawyer for the soldiers, two of whom were captains, said he would appeal against the sentence, which was handed down on Wednesday by the military tribunal in DR Congo's North Kivu province.

In addition to the 25 who received death sentences, one soldier was given a 10-year prison sentence and another was acquitted.

In May a military court in the city of Goma sentenced eight soldiers to death for "desertion" and "cowardice" when fighting rebel forces. They, too, are appealing against their sentences.

The M23 rebels have over the last few days captured several towns, including the strategic town of Kanyabayonga.

Neighbouring Rwanda is widely accused of backing the M23, but the government in Kigali denies it.

The UN has said that the current situation in North Kivu is "particularly concerning".

In the past week more than 150,000 civilians fled their homes, it said, worsening a humanitarian crisis in a region where 2.8 million people had already been displaced.

North Kivu is also "perilous" for humanitarian workers, the UN added.

On Sunday two aid workers with the charity Tearfund were killed after their convoy was attacked in the town of Butembo.

The army's fight against the M23 and other rebel groups in the east has long been hampered by the disarray within its ranks.

The army is seen as unprofessional and badly disciplined. Soldiers complain of poor pay and a lack of equipment.

Both the UN and regional states have troops in DR Congo to support the army, but they have failed to stem the violence.

M23 fighters are said to be well-armed and disciplined.

The rebel group began operating in 2012 ostensibly to protect the Tutsi population in the east of DR Congo, which had long complained of persecution and discrimination.

Despite Rwanda's denials, UN experts - along with France and the US - say the M23 is supported by President Paul Kagame's government.

Additional reporting by Emery Makumeno in Kinshasa