Libya's interim government has been struggling to control armed groups, especially those active in Tripoli [AFP]

At least two people have been killed and six others injured in the Libyan capital after two groups of armed men clashed over a dispute centred on the imprisonment of a member of one of the groups.

Witnesses on Tuesday told Al Jazeera a group of fighters from Misrata had clashed with members of another group in Tripoli who had taken one of their members prisoner.

The fighting occurred on Saeedi Street, near the site of the old interior ministry building, Al Jazeera's Imran Khan reported from Tripoli.

"Apparently what's happened is that one of the brigades from Misrata had a member of theirs arrested. They went in to then get that member out from the old ministry of the interior building, and that's when the clashes broke out," our reporter said.

According to the Associated Press, the man was being held on suspicion of robbery. 

Witnesses said members of the Tripoli militia arrested six Misrata men, brought them inside the council building, beat them up and detained them. The Tripoli council is affiliated with the National Transitional Council (NTC).

A top Misrata commander managed to mediate the release of all the men except for the one arrested for robbery and a second attempt to free the man by opening fire on a building was made by another group of Misrata fighters.

Fighting for control

The Libyan defence and interior ministries said that reinforcements were being sent to the area of the violence to try and control the situation.

"The big fear that most Libyans have here is about security. They're very worried about these groups being out on the street with guns, and they're very worried that incidents can quickly escalate. And that's what we're seeing here today," our correspondent said.

"It's very difficult for the ruling NTC and the interim government to try and control the brigades that are out on the streets, because they're simply entrenched in their positions and they have no choice. You have to realise that if you want security in this country and ... you don't have a fully functioning police force ... then you rely on these armed brigades."

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Disparate groups of former revolutionary fighters have clashed repeatedly since the end of the eight-month civil war that toppled Muammar Gaddafi's government in October.

Disbandment of these armed groups, which are divided by the regions where the operate, has posed a challenge to Libyan authorities.

While playing a vital role in overseeing security of key state institutions in the capital, the uncontrolled ownership of weapons and the absence of a central security administration has given the militias a free hand in ruling areas under their control.

Also on Tuesday, Mustaf Abdul Jalil, the NTC chair, appointed Yousef al-Manqoush as head of the armed forces in the first significant move to build a new Libyan military.

"A decision was issued today by the National Transitional Council to appoint Mr Yousef al-Manqoush chief of staff," the official told the Reuters news agency.

Manqoush is reportedly a retired army general who joined efforts to oust Gaddafi from his 42-year rule.

Source: Al Jazeera and agencies