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Libyans have been marking the anniversary of the uprising that led to the overthrow of Col Muammar Gaddafi after his rule of more than 40 years.

Celebrations have been taking place across the country, including in the capital Tripoli and in the eastern city of Benghazi, where the revolt began.

The White House congratulated Libyans but urged the new government to protect "the rights of all the Libyan people".

But the anniversary comes amid fears of continuing instability in the country.

Hundreds of militias are roaming the country unimpeded and observers point to an institutional void.

Libyan interim leader Mustafa Abdul Jalil on Thursday vowed a tough response to anyone who threatened national security during Friday's celebrations.

The White House said in a statement that the revolutionaries had a "responsibility to protect their freedoms by working with the government to establish stability, peace and reconciliation".

Meanwhile members of Col Gaddafi's former government outside Libya have told the ´óÏó´«Ã½ they are starting a political movement aimed at radical change in the country.

Friday 17 February marks one year since the first major demonstration against Col Gaddafi's rule in Benghazi, which became the rebel stronghold.

The uprising quickly spread around the country and led eventually to Nato's military intervention in the conflict. Col Gaddafi was killed in his hometown of Sirte on 20 October.

No official celebrations were organised, as a mark of respect for the thousands who died in the battle for Libya, but locally arranged events have been taking place.

Spontaneous commemorations began in Benghazi on Thursday, with residents setting off firecrackers, honking car horns and flashing "V for victory" signs.

On Friday, mothers in the city held pictures of their sons killed in the fighting, while singers and poets performed for the crowds, AFP reports.

Addressing crowds in Benghazi, interim Prime Minister Abdurrahim al-Keib said, quoted by Reuters: "We promise to find Gaddafi loyalists who are abroad, who were involved in killing or stealing Libyan money."

"We promise to build up our national army ... Let's stay united until we reach the safe land," he added.

In the capital Tripoli and other cities, roadblocks were set up to search for any attempt to disrupt the festivities.

Around 2,000 people gathered after Friday prayers in Tripoli's Martyrs' Square, where the celebrations had a carnival atmosphere, the ´óÏó´«Ã½'s Gabriel Gatehouse reports.

Only small numbers of armed men were in evidence among the crowds, he adds.

Tripoli resident Naima Misrati told AFP news agency she was celebrating the freedom the revolution had brought her.

"I have no words to describe my happiness. There is joy everywhere in Tripoli," she said.

"Despite the problems that remain in the country, this is an amazing day and we want to celebrate," Sarah, an engineering student celebrating with friends in central Tripoli, told Reuters.

"Just look at what was achieved in this past year."

In a TV address on the eve of the anniversary, Mr Abdul Jalil insisted his government had "opened our arms to all Libyans, whether they supported the revolution or not".

"But this tolerance does not mean we are incapable of dealing with the stability of our country," he warned.

"We will be tough towards people who threaten our stability. The thuwwar [brigades of former rebel fighters] are ready to respond to any attack aimed at destabilising" the country, he added.

Many of those celebrating in Tripoli today say they trust the thuwwar to protect them, but the government's lack of control over the fighters is seen as one of the central factors in Libya's continued instability, our correspondent reports.

Gunfights between rival militias can be heard in Tripoli and many other Libyan towns and cities almost every night, he adds.