At least 13 people were killed and another 130 wounded in Tripoli on Friday when gunmen opened fire on protesters.
The demonstrators had marched to the headquarters of the Misrata militia to demand that they leave the Libyan capital.
Tripoli council leader Saddat al-Badri said they were not armed.
The BBC reports the government is struggling to contain numerous militias who control parts of the country. Parliament is paralysed by divisions between secular and Islamist forces.
There have been increasing demands from civilians that the militias - which emerged during the 2011 revolution - disband or join the army. A deadline of the end of the year has been set by the interim government in Tripoli.
The BBC reports the militia was involved in clashes in the capital last week which left two people dead.
Last month, Prime Minister Ali Zeidan was briefly seized by a militia group in Tripoli.