The number of people displaced within Libya has almost doubled from an estimated 230,000 last September to more than 434,000 amid escalating fighting this year, a statement of UN High Commissioner for refugees (UNHCR) said on Tuesday.

"The internally displaced comprise 83,697 families, according to countrywide data collected by UN High Commissioner for refugees (UNHCR) and its partners," the statement said.

The numbers could be higher, warned UNHCR, but with limited access, the agency relies heavily on local partners, who are themselves unable to reach all affected areas because of a volatile situation.

The largest bloc, about a quarter of the internally displaced population (105,000), is located in the eastern city of Benghazi as a result of fighting in the coastal city, UNHCR said.

The conflict has also undermined the security of civilians and prevented the safe return of displaced people in Misrata, Tripoli, Warshafana and the Nafusa Mountains in the west, and Awbari in the south.

Libya, a major oil producer in North Africa, has been witnessing a frayed political process after former leader Muammar Gaddafi was toppled during the 2011 political turmoil.

The country is now deadlocked in a dogfight between the pro-secular army and Islamist militants, which has caused a security vacuum for homegrown extremism to brew.