Two Kenyan human rights activists have gone missing in Uganda after reportedly being abducted by armed men while attending opposition leader Bobi Wine's campaign event.

Bobi Wine strongly condemned the "abduction" of Bob Njagi and Nicholas Oyoo, saying the pair had been "picked up mafia-style" at a petrol station and driven off to an unknown destination.

Ugandan police spokesman Kituma Rusoke told the BBC the two were not in their custody. Kenya's Michael Muchiri said he was not aware of the matter.

Bobi Wine, a pop star whose real name is Robert Kyagulanyi, is running for the presidency in next year's elections, challenging President Yoweri Museveni, 80, who has held power since 1986.

Bobi Wine said the two Kenyans were being targeted by the Ugandan government for associating with him.

"We condemn the continuing lawlessness by the rogue regime and demand that these brothers are released unconditionally! The criminal regime apparently abducted them simply for associating with me and expressing solidarity with our cause!" he posted on X.

Kenyan rights group Vocal Africa has also condemned the reported abductions and demanded their unconditional release.

Mr Rusoke said "those fellows are not in police custody. Reach out to any other [security] agency maybe, just in case".

When contacted by the BBC, army spokesperson Felix Kulayigye said he could not speak about the matter because it was an allegation involving non-uniformed "security operatives".

He also tasked Bobi Wine to prove the allegations of abduction and which security agency was involved.

Ugandan security agencies have often been accused of orchestrating the detention of opposition politicians and supporters while not in uniform. Some of those arrested have later resurfaced in court facing criminal charges.

A fellow activist who witnessed what happened on Wednesday afternoon said that four armed men forced the pair into a vehicle and sped off.

"There were four of them. There was also a lady who was seated in front; they took Bob and Oyoo Ochieng, who is the secretary general of the Free Kenya Movement," the witness, who wanted to remain anonymous for security reasons, told Kenya's Citizen TV.

He said both were unreachable on phone and their whereabouts were unknown.

Videos shared online show Njagi actively participating in Bobi Wine's campaign, and appears on stage beside the opposition leader.

The activists had reportedly travelled to Uganda on Monday with some Ugandans before linking up with the campaign.

Njagi was also picked up in Kenya last year by masked men during a wave of abductions believed to have been targeting government critics in the country.

He remained missing for over a month before resurfacing, after a court ordered police to produce him. He later recounted the harrowing conditions in captivity - isolated and denied food for most of the days.

Their latest disappearances mirror past incidents involving politicians and activists across the East African region.

Earlier this year, Kenyan activist Boniface Mwangi and his Ugandan counterpart Agather Atuhaire were detained in Tanzania and held incommunicado for days before being abandoned at their respective national borders.

They later recounted being brutally mistreated, including sexual torture at the hands of the Tanzanian authorities – allegations which police dismissed as "hearsay".

Last year, another Uganda opposition figure, Kizza Besigye, mysteriously disappeared in Nairobi only to surface four days later in a military court in Uganda, where he faces treason charges.

The cases have since sparked widespread condemnation and concerns that East African governments could be collaborating to contain dissent.