A ceasefire in Yemen’s war was broken minutes after coming into effect, pro-government officials say.
The warring sides had agreed for a truce deal to be implemented in the port city of Hudaydah at midnight local time on Tuesday.
But there have been reports of sporadic clashes between the Houthi rebels and pro-government forces in the city, which is a vital gateway for aid.
The rebels have reportedly shelled government forces in eastern Hudaydah.
One pro-government official told AFP news agency clashes were ongoing.
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Both sides agreed to the ceasefire at United Nations-sponsored talks in Sweden last Thursday, and some hoped it would be the starting point to bringing nearly four years of civil war to a close.
But the truce was delayed on Friday following reports of strikes and fierce clashes.
Hudaydah, 140km (90 miles) west of the capital Sanaa, was Yemen’s fourth-largest city and a major economic hub before rebels took control of it in late 2014.
Since June it has been under assault by a Saudi-led coalition backing the pro-government troops.
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As a port, it is also a lifeline for just under two-thirds of Yemen’s population, who rely almost entirely on imports for food, fuel and medicine.
More than 22 million Yemenis need some form of aid, and eight million do not know how they will obtain their next meal.