Yemeni security officials say fighting has erupted in the key port city of Hodeida, killing at least eight people, including civilians.

Officials say the clashes began overnight and continued into Monday, leaving fires burning on the main front lines in the city's east and south, while exchanges of artillery fire shook the beleaguered city.

The officials spoke on condition of anonymity, as they were not authorized to brief journalists.

The new fighting could jeopardize the U.N.-brokered December cease-fire in Hodeida between Houthi rebels and Saudi-backed government forces.

Hodeida is the main entry point for humanitarian aid to Yemen, where nearly four years of war has spawned the world's worst humanitarian crisis.