CAIRO, Dec 23 (Aswat Masriya) - Egypt's foreign ministry demanded on Tuesday swift investigation by Libyan authorities into the killing of an Egyptian doctor and his wife, and bringing the perpetrators to justice.

Unidentified assailants killed a Coptic Egyptian doctor and his wife in the central costal city of Sirte and kidnapped their daughter, State-run MENA reported on Tuesday.

The ministry said in a statement that it is following up with news of the Egyptian nationals’ death, adding that there is coordination with the designated Libyan authorities concerning the incident.

It reiterated its warning to all Egyptians residing in Libya, calling on them to avoid any conflict areas. It renewed its travel alert to the neighbouring country, urging those travelling to Libya to secure a visa from the Libyan embassy prior to their travel.

Militant fighting in Libya has recently intensified in measures unprecedented since the overthrow of late Libyan President Muammar Gaddafi in 2011. Army general Khalifa Haftar declared war on Islamist forces within Libya since May.

Two Egyptians were killed in western Libya on December 14, and four others were injured in clashes between the Libyan army and Islamist militants near the Libyan border with Tunisia.

Several Egyptians had been killed and kidnapped during the unrest in Libya. Most of the Egyptian nationals working there have been evacuated from the conflict-torn country.