Shelling by Yemen's Houthi rebels damaged a silo and grain stocks at the Red Sea Mills in Hodeidah on Thursday, days after a visit by UN officials seeking to salvage thousands of tonnes of wheat stored there.
The rebels attacked with mortars and heavy machine guns while 28 staff were doing repair work at the mills, said Col Wathah Al Dubaish, spokesman for the joint pro-government forces in Hodeidah.
"The Houthi shelling created a big hole in one of the silos, damaging large quantities of wheat stored in it. Mortar shells also damaged some of the equipment at the facility and forced employees who have been doing maintenance on the generators since Sunday to stop their work," Col Al Dubaish told The National.
He said the workers had also been repairing damage to the silos caused by Houthi shelling last year.
The UN's World Food Programme said attacking the facility was "unacceptable".
"Any damage to humanitarian food stocks, whether deliberately targeted or as collateral damage, is unacceptable when millions in Yemen continue to suffer from crippling shortages of food," WFP spokesman Herve Verhoosel said in Geneva.
"All workers at the site are accounted for and no one was injured. We are confirming if any wheat was damaged. The area is now calm and work has resumed at the Mills," he said.
The workers arrived at the mills last Sunday with a team of UN experts from the WFP, which is trying to save at least some of the 51,000 tonnes of wheat that has been stored in the silos since September last year. Access to the mills was cut off by fighting that flared up around the port city of Hodeidah that month.
The UN agency's officials were last able to visit the facility in February, when they concluded that they might be able to salvage about 70 per cent of the wheat stored there.
"More than two months have passed since that assessment and the wheat will have most likely further deteriorated in quality, particularly given the hot weather," Mr Verhoosel said earlier this week.
The UN hopes to mill and distribute the wheat from Hodeidah to alleviate widespread hunger caused by the four-year-old war between the Iran-backed rebels and government forces supported by a Saudi-led coalition.
The Houthi shelling came as the UN prepares to send observers to monitor the first phase of a ceasefire agreement for Hodeidah that requires the rebels to withdraw from the ports of Ras Issa and Al Saleef.
Col Al Dubaish said the monitors were expected to arrive in the port city after a meeting between the UN-appointed chairman the Redeployment Co-ordination Committee, Danish Lt Gen Michael Lollesgaard, with government representatives in Aden on Saturday.
Amid UN efforts to implement the ceasefire in Hodeidah, the entry point for about 70 per cent of Yemen's food imports and humanitarian aid, the Houthis opened a new front by attacking the southern province of Dalea last month.
Government forces in Dalea made several gains after heavy fighting on Friday, according to a source in the Security Belt force on the front lines.
“The joint forces launched a wide-scale attack against the Houthi forces in the early hours of Friday and made crucial advances in Kardah and Humar Qatabah and secured the Al Sheim highway," the source said.
The highway is the main link between Yemen's southern provinces and Sanaa, the rebel-held capital, and is used to supply government forces fighting the rebels on the Mureis front in north-east Dalea.
The central command of the government forces in Dalea on Friday declared a curfew the areas of Qatabah, Sanah and Shakhab between 9pm and 8am.
"This step was taken to prevent infiltration by the Houthis and to prevent the civilians who have not fled the areas of fighting from being taken as human shields by the rebels," an officer in the joint forces told The National.