Witnesses said troops stormed buildings occupied by the Pioneers, a much-feared force used by the Malawi Congress Party of the ailing President, Hastings Kamuzu Banda, to spy on Malawians and enforce obedience to one- party rule.
Violence subsided as night fell, but several vehicles were ablaze and soldiers ignored a government broadcast on state radio to return to their barracks, a Western diplomat said.
A resident who spoke on condition of anonymity said the main hospital in Lilongwe reported 20 people had died, most from gunshot wounds. He said armed soldiers marched on the Young Pioneers' headquarters, to protest against the killing of two soldiers by the group on Wednesday.
In that incident, Young Pioneers in the northern town of Mzuzu allegedly went on a drinking binge and opened fire on a regional government office, killing two government soldiers.
The diplomat said Malawi's ruling presidential council met yesterday and ordered the Young Pioneers be disarmed because of the killings.
Civilians cheered the soldiers for moving against the unpopular Young Pioneers, seen as a symbol of years of oppressive rule, according to the diplomat. The group's headquarters were looted and gutted by fire, he said.