The M23 rebel group has not received an invitation to peace talks with the Democratic Republic of Congo scheduled to begin in Doha on Friday, its leader Bertrand Bisimwa told reporters on Thursday.

M23 rebels seized eastern DR Congo's largest city Goma in late January as part of a rapid advance that has given them control of more territory than ever before.

US President Donald Trump's administration has mediated talks between DR Congo and Rwanda that Washington hopes will produce a sustainable peace.

Release of prisoners

Under a separate but parallel mediation effort hosted by Qatar, DR Congo and M23 signed a declaration of principles on July 19 in which they vowed to start negotiating a peace agreement no later than August 8 with the goal of reaching a deal by August 18.

Bisimwa told Reuters on Thursday, however, that M23 had not received an invitation to Doha and that for now there was no M23 delegation there.

Another rebel leader, speaking on condition of anonymity, told Reuters the group would not go to Doha.

An official with knowledge of the matter said there had been a delay in releasing prisoners, but that both sides were still working to implement the terms outlined in the declaration of principles.

Progress 'being made'

"This includes ongoing negotiations to establish a mechanism – with involvement from the International Red Cross – for the exchange of prisoners, which has taken longer than initially anticipated," the official said.

"However, progress is being made, and once there is an agreement on this point, implementation of the deal is expected to pick up pace."

A Congolese government official directly involved in the talks told Reuters that prisoners could only be released after an agreement – rather than the declaration of principles – is signed.

Tina Salama, spokesperson for Congolese President Felix Tshisekedi, said DR Congo was still participating in the Doha peace process and would attend any meetings scheduled.