RIYADH (AFP) - The Saudi-led coalition bombing Yemen on Monday blamed ceasefire violations by rebels for the resumption of air strikes against them.

"They did not respect the humanitarian pause. That's why we do what is necessary to be done," said Brigadier General Ahmed al-Assiri. "There is an operation in process."

The Arab-dominated coalition resumed the bombing an hour after the five-day truce ended at 2000 GMT on Sunday (4 am Singapore time Monday).

The pause was proposed by Saudi Arabia to allow urgently needed humanitarian aid into Yemen.

"These militia did not stop their fighting. They continued to attack borders, to attack cities in Yemen," Assiri said, adding there was "a very big change on the ground" during the pause.

He accused the rebels of moving missiles with a range of about 70 kilometres towards the border with Saudi Arabia, said there was shelling "every day" of the Saudi boundary zone, and the rebels "hijacked" food and fuel aid in Yemen.

The coalition has been bombing the Iran-backed Shiite Huthi rebels since late March, in an attempt to stop their advance after they seized the capital Sanaa and swept across many other regions.

Analysts say the air strikes have failed to push back the Huthis.

Asked about the possibility of another truce, Assiri said: "When we talk about ceasefire it should be a negotiation between two parties but those militia, since 2216, reject everything."

He was referring to a UN Security Council resolution which in April imposed an arms embargo on the rebels and demanded they relinquish seized territory.