Libyan Prime Minister Ali Zeidan has been seized by armed men from a hotel in the capital, Tripoli, reports BBC.
Mr Zeidan was taken at dawn "by gunmen to an unknown place for unknown reasons", said a statement on the government's website.
The details of the incident are unclear - sources say Mr Zeidan was arrested by an anti-crime department militia, but others that he had been kidnapped.
On Tuesday he called on the West to help stop militancy in Libya.
In an interview with the BBC on Monday, Mr Zeidan had said Libya was being used as a base to export weapons throughout the region.
Last month Mr Zeidan visited the UK and appealed for British help to remove weapons from the country amid fears of increased arms smuggling to Syria.
In April he urged Libyans to back their government in the face of "people who want to destabilise the country".
He also complained at that time of other attacks and "acts of sabotage" carried out by separate groups, against the interior ministry and national TV headquarters.