Yemeni security officials and eyewitnesses say that fighting has erupted in the key port city of Hodeida, the first significant clashes since warring sides agreed to a U.N.-brokered cease-fire deal in December.

They say the combat began overnight into Sunday, 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 weren't authorized to brief journalists, while witnesses did so for fear of their safety.

The fighting comes days after the internationally recognized Yemeni government, along with allies Saudi Arabia and the United Arab Emirates, accused the Houthi rebel foes of breaking the cease-fire and refusing to withdraw their forces from the city in line with the December agreement.