Gunmen kidnapped the deputy foreign minister of Libya's internationally recognised government yesterday, the interior minister said.

As sporadic factional fighting continued in several parts of the country, six people were killed when rockets hit residential houses in the city of Benghazi on Sunday, medics said.

The kidnapping of Hassan al-Saghir happened in the eastern city of Bayda -- near where the officially recognised government has been based since being ousted from the capital in August. Gunmen snatched the deputy minister from his hotel, Interior Minister Omar al-Zanki said.

Kidnappings have become frequent in the North African country, where two governments and parliaments, allied to different armed factions, are vying for legitimacy and control four years after the ousting of Muammar Gaddafi.

Abdullah al-Thinni, the internationally recognised prime minister and his cabinet have been based in the east since a group called Libya Dawn seized Tripoli in August and reinstated the old assembly known as General National Congress.

The struggle has been complicated by a separate battle between army forces allied to Thinni and Islamists in Benghazi, the country's second largest city.

As well as the six dead, 20 people were wounded when rockets hit residential buildings in the al-Lithi district of Benghazi which the army has been surrounding for weeks to chase fighters of the Ansar al-Sharia Islamist group, medics and military officials aid.

Salim al-Naili, a special forces battalion commander, accused Ansar al-Sharia of having fired the rockets.

The army has merged its force with the troops of general Khalifa Haftar who declared in May his own war on Islamists.

The alliance now controls much of the port city but critics say Haftar's use of war planes and helicopters has damaged many buildings and caused civilian casualties.