The head of the Libyan rebels' armed forces and two of his aides were killed by gunmen on Thursday, creating a power vacuum at the top of the opposition military hierarchy and raising questions about who was responsible.
The killing, in circumstances that remain murky, has shaken Western confidence in the movement to oust Libya's leader, Muammar Gaddafi, and constitutes a blow for the US, Britain, France and other countries backing the under-trained and divided opposition alliance.
Abdel Fattah Younes was killed after being summoned to the de facto rebel capital of Benghazi to appear before a judicial inquiry, opposition leader Mustafa Abdul Jalil announced at a press conference late on Thursday night.
He told reporters that rebel security had arrested the head of the group behind the killing but had not found the dead men's bodies.
By Friday, however, it appeared that the bodies had been found and returned to their relatives. Tens of thousands of people gathered in Benghazi's central Courthouse Square - renamed Tahrir Square by the opposition - to observe Friday prayers and mourn Younes.
They carried coffins bearing the deceased through the square and chanted, "The blood of martyrs will not be spilled for nothing", under the nervous gaze of security forces.
Abdul Hakim, a nephew of Younes, told the Reuters news agency that Younes' body had been returned to his family on Thursday, burned and bearing bullet wounds. He said Younes had called to say he was coming to Benghazi around 10am Thursday morning.
Questions over killing
Rebel security reportedly arrived at Younes' operations room near the rebels' eastern front and arrested him and his aides early on Thursday.
Security officials said at the time that Younes was to be questioned about possible ties to Muammar Gaddafi's regime.
Younes was Gaddafi's interior minister before defecting to the rebels early in the uprising, which began in February.
Jalil said that Younes had been summoned for questioning regarding "a military matter". He said Younes and his two aides, a colonel and a major, were shot before they arrived for questioning.
Al Jazeera's Tony Birtley, reporting from Benghazi, said that the body had not been handed over yet.
"One of the assailants was captured. [The groups] were described as pro-Gaddafi units."
"Now there is a hunt going in Benghazi to find those people," he said.
Jalil called Younes "one of the heroes of the 17th of February revolution", a name marking the date of early protests against Gaddafi's regime.
He did not say Gaddafi's forces were directly responsible for Younes's killing but said Gaddafi was seeking to break the unity of rebel forces. He also issued a stiff warning about unaffiliated "armed groups" in rebel-held cities, saying they needed to join the fight against Gaddafi or risk being arrested by security forces.
'A man who was a target'
After Jalil finished his remarks, without taking questions, there were reports of fighting and gunfire in and around the Tibesti Hotel, where the press conference was held.
A witness told the AFP news agency that supporters of Younes grouped outside the Tibesti, fired their weapons in the air and attempted to enter the hotel, where they were confronted by NTC security.
Some of the men shouted, "You killed him", in reference to the NTC.
"[Younes] is a man who was a target," Birtley said. "It is a question of who was he targeted by: Pro-Gaddafi loyalists or people on the opposition side who didn't actually like his politics because there were questions about where his loyalties truly lay."
"This was a man who was the interior minister for Gaddafi. He was a personal friend for 40 years and that friendship shone through."
"When I [interviewed] him, he said he changed sides because the Gaddafi he knew was not the Gaddafi that was leading the country any longer."
Within an hour, at least three loud explosions shook the centre of the Libyan capital, Tripoli. Two explosions were heard at 10:20pm local time, followed by another blast several minutes later, as Libyan television reported that planes were flying overhead.
Tripoli has been the target of repeated NATO air raids.
Meanwhile, Libyan opposition fighters in the western mountains launched attacks on several government-controlled towns, hoping to push out loyalist troops and open a route to the border.
The attacks began around dawn as rebels descended from around the towns of Nalut and Jadu in an attempt to expel forces loyal to Libyan leader Muammar Gaddafi from the Nafusa mountain foothills.
By midday local time, rebels had taken and lost the town of al-Jawsh and reached the outskirts of Ghazaya, a significant base for Gaddafi's troops near the Tunisian border.
Four rebels were killed and 10 injured, while 18 loyalist troops were captured, according to opposition sources.
Al Jazeera's James Bays, who approached al-Jawsh with the rebel advance, said fighters initially took the town and moved on but were caught by a surprise counterattack.
"At the very time that they have the setback death or Mr Younes, they had a military victory in taking a large area here near the Tunisian border," our correspondent said.
"But a short time ago they had reports that possibly there was a Gaddafi counter-offensive coming down the road," he said.
Despite hitting al-Jawsh with artillery fire and attempting to clear out Gaddafi's troops, some 2,000 regime forces apparently remained in town, while others fired Grad rockets after the rebels entered.
Farther west, Ghazaya had been bombarded by rebel tanks and "long-range guns" throughout Wednesday night in preparation for the attack, an opposition source said.
The fight for Ghazaya continued into Thursday afternoon, and rebels claimed to have seized the nearby town of Takut.
A rebel spokesman in Jadu claimed rebels had taken Ghazaya, but that claim was not confirmed by other sources.
Trucks carrying hundreds of fighters were involved in the operation at al-Jawsh, Bays said.
It appeared to be the largest attack by opposition fighters in the Nafusa Mountains since the conflict began.