No-one appeared to have been hurt among dozens of supporters of Gaddafi, who was toppled in 2011 and killed, dictatorship then giving way to today's chaos as two rival governments fight for power and Islamist militants build their influence.
The Gaddafi supporters waved pictures of the man who had ruled for 42 years, and demanded the release of his most prominent son Saif al-Islam, whom a Tripoli court sentenced to death in absentia last week for crimes during the uprising.
He has been held since 2011 by a former rebel group in Zintan, a region beyond Tripoli's control. Right groups say the verdict was riddled with flaws.
"Only God, Muammar and Libya!" the crowd chanted and waved the green flags of the old regime.
They dispersed after other residents, some of them carrying the Libyan national flag, opened fire.