Reports by several Ugandan papers seen by APA in Kigali quoted Ugandan Police as saying in a statement that the deaths occurred during security operations earlier this week.
It said that at least 65 people had been injured and about 350 arrested.
Ugandan media reports indicate that men dressed in civilian clothes armed with assault rifles were seen patrolling city streets and also fired bullets at protesters and anyone taking their pictures.
It is reported to be the worst violence to erupt on the streets of Ugandan cities since Bobi Wine was nominated as a presidential candidate.
The National Unity Platform (NUP) presidential candidate was arrested - for violating Covid-19 restrictions, according to police - in Luuka District on Wednesday. Ensuing mass protests in the country have paralysed transport and business.
The musician is among 11 candidates challenging President Yoweri Museveni - in power since 1986 - in the presidential election which will be held on January 14 next year.
Four other presidential candidates; (Rtd) Maj Gen Mugisha Muntu, (Rtd) Lt Gen Henry Tumukunde, Norbert Mao and Fred Mwesigye have suspended their campaigns in solidarity with Bobi Wine.
The NUP candidate was, by Friday morning, still detained at Nalufenya Police Station, in Jinja.
During the protests across the country, security forces were filmed firing tear gas and live bullets to disperse people in the capital, Kampala.
Angry demonstrators are seen burning tyres and rubbish in the streets and blockading roads in the Ugandan capital city Kampala