By Freya Berry
LONDON, Dec 14 (Reuters) - A dissident Ugandan general launched an opposition party in London on Saturday and said it was time for President Yoweri Museveni to end his 28-year rule, a fresh challenge to a leader who is now among the longest serving in Africa.
General David Sejusa, once a top intelligence official, fled to Britain in May after he was embroiled in a row about Museveni's son, who has risen rapidly through army ranks and some critics say is being groomed to take over from his father.
Museveni's son, Muhoozi Kainerugaba, has denied such a plan exists, while the 69-year-old president has not outlined his plans, although few doubt he will run again in elections in 2016.
"He's had enough time," Sejusa said on the sidelines of a meeting to launch his party, the Freedom and Unity Front.
"He can leave and go, and we start a new process of national healing. And we are organising ourselves, we are establishing a constitutional rule which he destroyed," Sejusa told Reuters at the London event that was attended by about 40 or so people.
At one point, a woman heckled Sejusa, saying he should answer for "war crimes" when he was in office. The general smiled calmly as the woman was escorted out while shouting.
Most Ugandan parties are small and have limited voice. Analysts say anyone seeking to challenge Museveni's grip would likely need some support in the military, which was built up around the rebel group that the president led through the bush to power.
Museveni, who came to power in 1986 amid popular support and high hopes from donors, has been praised for restoring order in Uganda but has faced mounting opposition from critics who say he has become another African strongman who smothers dissent.
Museveni initially banned all parties, leaving his National Resistance Movement - which he insisted was not a formal party - to dominate. He opened up politics in 2005 to allow parties to form, while also scrapping presidential term limits.
Asked whether he wanted to be president himself, Sejusa, an ex-fighter in the rebellion that brought Museveni to office, said it was "a waste of time" to run against Museveni in the current system.
In October, Museveni dared Sejusa to try to overthrow him and said anyone using violence would be stopped. "If Sejusa wants to use force, let him come," he told a news conference.
When Sejusa was asked if he would use force to bring change, he said: "It's not so much that we want to do so. But if he continues to unleash terror on the population ours will be self defence."
The most prominent opposition group is the Forum for Democratic Change, whose former leader, Kizza Besigye, made three failed runs for the presidency and complained of voting abuses each time.
Besigye, another former Museveni ally, has frequently been detained by police even since stepping down from party office. His supporters say it is part of a broader clampdown on dissent. (Writing by Edmund Blair in Nairobi; Editing by Rosalind Russell)