Former Congolese President Joseph Kabila has announced a movement to "save" his country, after a meeting with other opposition leaders in Kenya's capital Nairobi.

The meeting, held on Tuesday and Wednesday, resolved to rally Congolese to oppose the "dictatorship" of President Félix Tshisekedi, according to a document seen by the BBC.

Congolese government spokesman Patrick Muyaya dismissed it as a "non-event", and a meeting of "fugitives and convicts". Kenya's foreign ministry has not responded to the BBC's request for comment.

Kabila was recently sentenced to death back home for war crimes and treason. He rejected the charges as "arbitrary" but did not appear in court to defend himself.

Since May, his whereabouts have not been known until earlier this week when images of him in Nairobi surfaced on social media.

The meeting in Nairobi included former DR Congo Prime Minister Augustin Matata Ponyo, who was sentenced to a decade in prison for corruption in May.

Participants warned that DR Congo was facing a deepening crisis due to the government's rejection of inclusive dialogue and poor economic governance.

They criticised Tshisekedi's failure to enact policies to address urgent public needs, despite his full control of state power.

"From every corner and crevice of Congo, let us unite and take daily actions to save the DR Congo. Every gesture matters and will count toward victory and dignity," they said in the 14-point declaration bearing the signatures of the leaders of 12 opposition and civil society groups.

They also denounced the "arbitrary detention of political leaders... [and] all the unfair judgments handed down by courts and tribunals against opposition leaders" and critics of the government.

They vowed to launch a diplomatic offensive to alert the international community to DR Congo's crisis.

The Congolese government has previously expressed concerns over Kenya hosting opposition figures linked to the M23 rebels, who have seized large parts of eastern DR Congo, sparking a diplomatic row.

In 2023, opposition figure Corneille Nangaa announced the formation of the opposition Alliance Fleuve Congo from Nairobi. The group includes opposition figures and the M23.

Kabila ruled DR Congo from 2001 until 2019, after succeeding his father Laurent, who was shot dead in 2001.

Kabila backed Tshisekedi in the disputed elections of 2019, but they later fell out and Kabila went into self-imposed exile in 2023.

Tshisekedi accused Kabila of being the brains behind the M23 rebel group in eastern DR Congo and senators stripped him of his legal immunity, paving the way for his prosecution in a military court that led to the death sentence two weeks ago.

In April this year, the former president said he wanted to help find a solution to the deadly fighting in the east and arrived in the M23-held city of Goma the following month. He had not been seen in public since then until this week.

The meeting in Nairobi came as the Congolese government signed an agreement with the M23 in Doha to set up a way of monitoring their ceasefire.

Both sides have accused the other of breaking the deal.