Quilliam, a group that studies Islamists, said in a report that while Libya had jihadist groups, "they are nowhere near as powerful or as widespread as the Gaddafi regime has claimed".
"That said, the breakdown in Libyan government control over much of Libya, combined with the ongoing fighting in many parts of the country, clearly gives jihadists and extreme Islamists more scope than ever before to operate in Libya," it said.
It also said the amount of weapons becoming available in Libya as a result of the war was a serious cause for concern.
No Western officials take seriously Gaddafi's allegation that al Qaeda set off Libya's revolt, but there are growing indications of concern among Western governments that Islamist fighters may be operating with opposition forces.
NATO's top operations commander, Admiral James Stavridis, said in Washington on Tuesday that intelligence on the rebels had shown "flickers" of al Qaeda or Hezbollah presence but there was still no detailed picture of the emerging opposition.
Quilliam said that while the picture of Islamist activity in the revolt was incomplete, it believed most of Libya's community of former armed Islamists supported the rebel National Council leadership, which has called for Western assistance.
One of the report's authors is Noman Benotman, a former leader of the Libyan Islamic Fighting Group (LIFG), which waged a failed armed insurgency against Gaddafi's rule in the 1990s.
The report lists several militant Islamist groups and details their ability to gain a following in Libya.
Al-Qaeda's Central leadership
The group's senior leaders have "few, if any, active operatives in Libya". To overcome this, al Qaeda has issued statements about Libya to try to inspire Libyans to create their own local version of al Qaeda.
One spokesman was Atiyyah Allah, a Libyan al Qaeda member since 1989 now based in the Afghanistan-Pakistan region.
Al Qaeda in the Islamic Maghreb (AQIM)
AQIM, al Qaeda's north Africa arm, sees the instability in Libya as a chance to move operatives in. As many as 40 Libyans have joined AQIM outside the country in recent years, even though non-Libyans still dominate the group's leadership.
In early January, AQIM sent two of its Libyan members to Libya from northern Mali via southern Algeria, Quilliam said.
Arriving in Ghat, a town in Libya's south-west on Jan. 15, they were involved in a shootout with local Libyan security forces, killing one policeman, before being killed themselves, in AQIM's first known armed operation in Libya.
AQIM raised its involvement after Libya's revolt broke out in mid-February, posting a propaganda video purporting to show AQIM sending four jeeps loaded with arms into Libya.
The former LIFG
Once one of the largest Arab jihadist groups, the LIFG largely rejected al Qaeda's concept of global jihad and focused mainly on establishing an Islamic state in Libya.
By the early 2000s, however, the movement had largely been crushed. Al Qaeda announced a merger with it in late 2007, but the Libyan group rejected the move and embarked on a reconciliation process with the Libyan government which ended with the group disbanding itself in mid-2009.
Some former LIFG men are involved politically in the revolt and some are fighting against Gaddafi, Quilliam said.
For instance, a former LIFG veteran Khalid al-Tagdi was killed in battle on March 2 in Brega.
It is not impossible the international community's use of airstrikes may lead some individual ex-LIFG members to re-adopt hardline ideology, particularly if they are courted by al Qaeda.
Libya is home to a large number of militants who adopted Islamist violence independently of any formal group. The Libyan city of Darnah in opposition-held eastern Libya is a centre of so-called self-starter militants, Quilliam said.
According to the "Sinjar Records", a captured al-Qaeda list of foreign fighters in Iraq, more foreign jihadists travelled to Iraq from Darnah than any other city in the world.
Many who fought in Iraq were arrested on their return, and later freed on condition they renounced violence. It is not known how many others returned undetected by the govenrment.
Their whereabouts and activities are one of the main unknown factors in the Libyan conflict.
**Writing by William Maclean