Former rebel gunmen have freed Libya's prime minister after holding him for several hours.

He had been kidnapped in reprisal for the capture by US forces of a Libyan al Qaeda suspect in Tripoli, officials said.

A Reuters journalist  said protesters had opened fire at the building where Ali Zeidan was being held to demand that the group free the premier.

"The prime minister has been released," a government official said. A security source also said Zeidan was free.

Ali Zeidan said on Twitter that his captors had wanted him to step down.

"I am fine, thank God. If the aim of the kidnapping operation was for me to present my resignation, then I won't resign. We are taking small steps, but in the right direction."

Gunmen seized Ali Zeidan from the Corinthia Tripoli Hotel early this morning.

"The head of the government Ali Zeidan was taken at dawn this morning by gunmen to an unknown place for unknown reasons," the Libyan government said. 

Guards at the Corinthia said gunmen had taken Zeidan from the hotel but there were no shots fired or clashes during the incident.

A group of former Libyan rebels said it seized the Prime Minister because of his government's role in the US capture of a top al Qaeda suspect in the Libyan capital.

"His arrest comes after the statement by John Kerry about the capture of Abu Anas al-Liby, after he said the Libyan government was aware of the operation," a spokesman for the group, known as the Operations Room of Libya's Revolutionaries, said referring to the US Secretary of State.

The group later said he is "good health and will be treated well as a Libyan citizen."

He was being held at the Interior Ministry's anti-crime department. The group members, former rebels were working for the Interior Ministry to provide security in the capital.

A still from footage allegedly showing the Libyan prime minister during his kidnapping.[/attach]

Al-Arabiya television channel quoted Libya's justice minister as saying that Zeidan had been "kidnapped" and showed what it said were video stills of Zeidan frowning and wearing a grey shirt undone at the collar surrounded by several men in civilian clothes pressing closely around him.

CNN reported that 150 armed men turned up in about 35 cars and took the prime minister away.

MALTA CONCERN

Prime Minister Joseph Muscat in comments to the press expressed concern about developments in Libya and about the welfare of the Libyan prime minister, whom he described as a personal friend.

He said the government was keeping a close eye on developments. However the situation was fluid and one could not comment further at this stage, he said.

The US yesterday said it was moving 200 Marines to Sicily to be on standby in view of the situation in Libya after protesters called for attacks against American interests.

Ali Zeidan was in Malta last month when he signed an agreement to sell oil to Malta at preferential rates.