Ugandan protesters who said they would press ahead with a banned anti-corruption march on Tuesday are "playing with fire", the country's president warned.

"Some elements have been planning illegal demonstrations, riots," President Yoweri Museveni said in a televised address late Saturday.

Museveni has ruled the East African country with an iron fist since 1986.

He said the protesters included "elements working for foreign interests", without elaborating.

Earlier Saturday, Ugandan police had informed organisers it would not permit the planned protest in the capital Kampala as authorities had intelligence that "some elements were trying to take advantage of the demonstration to cause chaos in the country".

"Demonstrations can only be allowed under our mandate as long as they are not causing public disorder and disrupting lives of lawful citizens," Ugandan police operations director Frank Mwesigwa told AFP.

The protest organisers told AFP they vowed to press on with the demonstration regardless.

"We don't need police permission to carry out a peaceful demonstration," one of the main protest leaders, Louez Aloikin Opolose, said Saturday. "It is our constitutional right."

The protesters hope to take the march past parliament, which they accuse of tolerating corruption.

"Our starting point in the fight against corruption is parliament... and the demonstration is on irrespective of what police is saying," protester Shamim Nambasa said.

The NGO Transparency International ranks Uganda low on its corruption perceptions index. With the least corrupt countries ranking highest, Uganda comes in at 141 on the list of 180 countries.

The anti-corruption protesters have been keeping track of the sometimes deadly demonstrations that have shaken neighbouring Kenya for more than a month.

The Kenyan protests, beginning as peaceful rallies against controversial tax hikes, turned into a wider anti-government campaign, with disgruntled activists also seeking action against corruption and alleged police brutality.

At least 50 people have been killed and 413 injured since the demonstrations began on June 18, according to the state-funded Kenya National Commission on Human Rights.