The Saudi-led military coalition fighting in Yemen will not renew a two-day ceasefire in the ongoing war, a spokesperson has told the al-Arabiya TV network.
The 48-hour ceasefire, which led to a pause in nearly two years of fighting, was unilaterally announced by the Saudi coalition on Friday, but it failed to halt the fighting between the coalition and the Iran-aligned Houthi fighters in the war-ravaged country.
Each side has blamed the other for violating the ceasefire.
Gulf Arab countries led by Saudi Arabia launched the military offensive to back President Abd-Rabbu Mansour Hadi's government in March 2015, as the Houthis and troops loyal to former President Ali Abdullah Saleh advanced towards Hadi's headquarters in Aden.
The 20-month conflict has killed more than 10,000 people and displaced more than three million.
Residents in the capital Sanaa said that Saudi-led coalition jets had bombed army bases on a mountain overlooking the city earlier on Monday, and the force of the explosions had shaken buildings in several city neighbourhoods.
Sanaa is controlled by the Houthis, who still hold vast swaths of Yemen. Despite Saudi-led forces gaining territory from the northern Yemeni rebels, they have not succeeded in restoring Hadi to power.
Major General Ahmed Asseri, the coalition spokesman, told Al Jazeera on Sunday from Riyadh that air raids had been launched in response to violations by the Houthi rebels who control most of Yemen.
"We told them that if they move their troops on the ground, if they try to gain position, there will be a response. This is what we are doing," Asseri said.
"There are people on the ground we have to protect. We have the Yemeni national army, we have the population in the area."
He said the Houthi rebels "keep firing on civilian positions" in the city of Taiz.
Asseri accused the Houthis of 180 violations in the first 10 hours of the ceasefire.
Rajeh Badi, a spokesman for Yemen's exiled government, declined to comment on the proposed deployment of observers but said Houthi violations had made extending the truce meaningless.
A spokesman for Yemen's pro-Houthi military said in a statement that coalition and pro-Hadi forces had violated the truce 114 times and that its forces had "reserved the right to respond to violations and abuses of aggression".
Visiting neighbouring Oman last Tuesday, the US Secretary of State John Kerry announced that both sides had agreed to a deal whereby the Houthis would quit Yemen's major cities and the factions would form a national unity government.
But Hadi's government rejected the announcement that the warring parties had agreed to an open-ended truce and to work towards forming a joint government.
It said it was not consulted about the accord and objected to demands that the Houthis withdraw from cities they had captured since 2014.
The Houthis have also said the ceasefire was designed to undermine the agreement reached in Oman.