Unidentified assailants fatally shot the mayor of Libya's third-largest city, Misrata, late on Sunday, ambushing his car inside the city, security officials said.
Gunmen chased the car of Mayor Mohamed Eshtewi after he left Misrata airport following his arrival on a plane from Turkey, a security official said, adding it was unclear who was behind it.
The city hospital said it had received the mayor's body bearing gunshot wounds.
His body was found dumped in the street. His brother was with him in the car and was wounded in the attack, a security source said.
UN envoy for Libya Ghassan Salame on Twitter denounced the killing and expressed his "profound sadness" over the news.
Britain's ambassador to Libya, Peter Millett, said he was "deeply saddened by (the) senseless murder".
In October, a bomb exploded at the city's court, killing about four people and wounding 40 others in an attack claimed by ISIS.
Misrata, almost 200 km east of Tripoli, is the gateway for food and other imports into Libya and the country's only tax-free zone. It is one of the few places still frequented by foreign business people fearing poor security elsewhere.