The Iranian-backed Houthi fighters shelled targets inside Saudi Arabia despite the five-day truce announced by the Saudi-led coalition, Houthi-run media claimed.
Saudi Arabian-led coalition forces announced a humanitarian truce in Yemen, after weeks of their campaign against Iranian backed Houthi forces, taking effect on Sunday evening at 11:59pm local time (0859 GMT), the Saudi state news agency SPA said
Just hours after announcing the truce, the Houthi forces shelled the northerly Al Tawal region on the Saudi border, and the Saudi forces had retaliated, Saudi-owned Al Arabiya television reported.
The Houthi-run Saba news agency said that the Houthi militias, and allies loyal to former president Ali Abdullah Saleh, had attacked Al Khawjarah and Al Maa'zab areas in the Red Sea province of Jizan with rockets and shells.
Ekhbariya, the Saudi state news broadcaster reported that Houthi forces had executed attacks in both the Marib and Taiz provinces.
According to Reuters, Mohammed Ali al Houthi, the head of the Houthi supreme revolutionary committee, said his part ”had not been formally notified of any ceasefire by the United Nations.”
"There is no positive or negative stance until the United Nations formally addresses us concerning the matter," he said.
On Sunday, UN Secretary General Ban Ki-moon urged all parties to suspend military operations during the ceasefire and refrain from exploiting it to move weapons or seize territory.
Five-day truce announced
The 5-day cease-fire came after at least 120 people were killed in Saudi air strikes in a residential town on the Red Sea coast on Friday.
The truce is expected to last five days to allow for desperately needed humanitarian aid to be delivered to war torn Yemen.
The statement on Saturday by the Arab coalition stressed that they would respond to any violation of the truce by the Houthis.
The UN has declared the situation in Yemen to be a level-three humanitarian emergency, the highest on its scale, after about 80 percent of the country’s population fell into the dire need for humanitarian aid.
Twenty million people in the country are in need of aid, 13 million are facing food shortages and 9.4 million are having difficulties accessing drinking water.
A ship carrying enough UN aid to feed 180,000 people for a month docked at the Yemeni port of Aden on Tuesday, having previously being prevented from doing so for almost four weeks, World Food Programme spokesman Peter Smerdon said.
"It's the first WFP chartered ship to berth in the port since the conflict erupted in late March," Smerdon said. "We have additional ships chartered which are on standby heading towards Aden carrying more food and fuel."
Aden airport works again
The first Saudi military plane landed down on Aden International airport in Southern Yemen on Wednesday last week, first arrival of a flight in the four-month long war in the port city.
More than 1,300 military humvees arrived last week to Aden through Bureiqah port to support the forces allying the exiled Yemeni President Abd Rabbuh Mansur Hadi.
Yemeni local fighters backed by Saudi-led air strikes wrested the port city and its airport from the Houthi rebels last week. The district of Khormaksar also fell under the control of pro-government militiamen.
Several exiled ministers and top intelligence officials - formerly based in Riyadh - successfully landed in Yemen's devastated southern city of Aden last week.
This is the first visit for Hadi’s government to Aden in three months, since the start of the Saudi-led air strikes against the Houthis in Yemen began in late March.
Around 20 million Yemenis are suffering from a lack of water and a million people have been displaced from their homes as a result of the armed conflict in the country.
More than 3,500 people, including 1,500 civilians and 365 children, have been killed in the conflict since March, according to the UN.