Several powerful blasts rocked Libya's capital on Tuesday, as the executive branch of Libya's rebel government was sacked in a political crisis a week after their military chief's assassination.

The explosions in the Fernej district of southwest Tripoli struck at between 1:00am (2300 GMT) and 2:00am, sending flames shooting into the night sky, an eyewitness reported.

They were followed by a series of smaller blasts, suggesting an arms depot had been hit. Two other explosions followed at around 6:00am, he said.

In the rebel capital of Benghazi in eastern Libya, Mustafa Abdel Jalil, chairman of the National Transitional Council (NTC), sacked the entire executive office of his government late on Monday, officials said.

He dismissed several top ministers -- including those responsible for finance, defence and information -- while calling for root and branch reform.

"Mr Mustafa Abdel Jalil has disbanded the executive office," spokesman Shamsiddin Abdulmolah said, adding that Prime Minister Mahmud Jibril would be tasked with creating a reformed body.

It was the latest dramatic phase in the turmoil sparked by the assassination of rebel military commander General Abdel Fatah Yunis -- amid his return to Benghazi under arrest in late July.

The NTC has come under fire for its role in events leading up to Yunis's death, as well as its handling of the aftermath.

Although details are sketchy and still under investigation, it is known that an arrest warrant was signed by senior NTC executive member Ali Essawy, raising allegations that the NTC unknowingly helped facilitate his murder.

Essawy was one of the most visible members of the rebel government -- the interlocutor for visiting foreign dignitaries.

The council has faced angry and sometimes violent protests from Yunis's tribe, as well as demands for reform from groups that were at the forefront of the uprising against Libyan leader Moamer Kadhafi that erupted in mid-February.

Jalil has vowed that an internal investigation into the NTC's management of the crisis would not flinch from apportioning blame. "No one is above the law, starting from the top of the NTC," he said.

Since the general's death, tribal tensions have come to the surface in a country where clans for decades have formed the basis for solving disputes in the absence of functioning judicial institutions.

Insiders have reported frequent clashes between the NTC, whose members were largely Libyan-based lawyers and former members of Gaddafi's regime, and the executive branch, the majority of whom were exiles.

On the ground, rebel fighters have been battling to defend gains in the west, in the face of an offensive by troops loyal to Gaddafi.

Rebels fighting at Zliten, 120 kilometres (75 miles) east of Tripoli, have admitted they were running low on ammunition as they struggled to hold off an assault by loyalist forces.

Abdul Wahab Melitan, a rebel spokesman in the port city of Misrata near Zliten, said pro-Gaddafi forces had launched an assault on their positions on Sunday in the Souk Telat area.

Four rebel fighters were killed and 40 wounded, he said. "The rebels lack ammunition to advance and we do not want to risk losing any ground."