Uganda's veteran president Yoweri Museveni warned that anyone breaking the peace would regret their actions as he formally started his bid for another term in office on Monday.

The 76-year-old, who is Africa's third-longest ruling head of state, is due to face Bobi Wine, a pop star turned opposition politician, in a February vote.

"I am hearing ... some people want to disturb our peace. Whoever tries will regret (it)," the former guerrilla leader said after the Electoral Commission accepted his nomination papers.

"For us we do not joke, we fought to bring peace," he told reporters in comments broadcast on television.

Supporters have praised Museveni for bringing in investment and bolstering the economy while opponents have accused him of crushing dissent and presiding over widespread graft - charges that he has repeatedly dismissed.

Lawmakers from his ruling National Resistance Movement (NRM) party voted to change the constitution in 2017, deleting a 75-year age cap on presidents that would have barred him from seeking re-election.

Officially he will be running for his fifth term in office - though he ruled for nine years without facing a vote after coming to power in 1986 following a guerrilla war.

Bobi Wine, Museveni's 38-year-old main challenger, is due to be named as the opposition National Unity Platform (NUP) party's presidential candidate on Tuesday.

The musician, who put out a song in the early days of the pandemic encouraging people to wash their hands, has built up a following among Uganda's younger voters - around 75% of the population is below 30.

Wine, whose real name is Robert Kyagulanyi, said dozens of police and soldiers stormed his party's offices in Kamwokya, a suburb of the capital Kampala, in October.

Police and the military have repeatedly dispersed his rallies. Supporters have been using his distinctive red beret as their symbol, but the government last year classified the item as military garb and banned its civilian use.