A standoff between two rival governments in Libya worsened on Thursday with the risk of fighting or territorial division as the parliament in the east swore in a new administration while the incumbent in Tripoli refused to cede power.

Addressing the parliament after taking the oath of office, Fathi Bashagha said he was studying all options to take over in Tripoli. The present prime minister there, Abdulhamid al-Dbeibah, has said he will not hand over control.

Armed groups affiliated with both sides have mobilised in the capital and foreign forces, including from Turkey and Russia, remain entrenched in Libya nearly 18 months after a ceasefire ended the last major bout of warfare.

Underlining the tense situation, Bashagha's office has accused Dbeibah of using force to try to stop his cabinet reaching Tobruk for the parliament session by closing air space and seizing three ministers who tried to travel by land.

Dbeibah's government has not responded to those claims, though airline sources said domestic flights were not operating and a statement from his defence ministry warned against any armed convoy moving without permission.

Libya has had little peace or security since the 2011 NATO-backed uprising against Muammar Gaddafi and it split in 2014 between rival governments based in Tripoli, in the west, and in the east where the parliament is based.

Neither the political nor the military coalitions that are crystalizing now exactly match those that fought from 2014 until a 2020 truce, but any new conflict would again likely pit eastern forces against a combination of western groups.

Dbeibah's government was put in place a year ago through a U.N.-backed peace process that was aimed at resolving political problems through an election, but the vote did not take place amid arguments over the rules.

Since then, the parliament has tried to take control of the process by saying Dbeibah's term had expired and setting a course towards a referendum on an altered constitution and then elections in 2023.

(With input from agencies)