The warring sides had agreed to a five-day pause to allow humanitarian organizations to get supplies to civilians caught up in the violence. But smaller scale clashes have continued since it went into effect late Tuesday
Aid groups say the lull has made a difference.
"Despite reports of heavy fighting in certain parts of the country, lifesaving supplies are reaching hospitals, health centers, affected communities and displaced people," UNICEF, the U.N. program that helps children and mothers, said Sunday.
But an intensification in violence is feared after the truce ends at 11 p.m. Sunday (4 p.m. ET).
In the conflict, Shiite Muslim rebels from the north of the country, known as Houthis
, are clashing with forces loyal to President Abdu Rabu Mansour Hadi, whom the Houthis ousted earlier this year.
A coalition of Arab nations led by Saudi Arabia is backing Hadi and has been carrying out a campaign of airstrikes on the Houthis and their allies since late March.
Complicating the picture, the Houthis have support from some Yemeni military units that remain loyal to Hadi's predecessor, Ali Abdullah Saleh.
Saudi Arabia fears that Houthi control of Yemen would strengthen the hand of its bitter regional opponent, Iran. But the exact nature of the links between the Houthis and the Iranian regime are unclear.
Yemen is also the stronghold of Al Qaeda in the Arabian Peninsula, which has taken advantage of the increased unrest to try to expand its reach.
Talks on the conflict, called for by Hadi, were scheduled to take place Sunday in Riyadh, Saudi Arabia
. But the Houthis and Saleh weren't expected to attend, making it uncertain what progress could be achieved. Hadi is currently in exile in Saudi Arabia.
Hundreds of civilians killed
The start of the Saudi-led air campaign against the Houthis intensified the conflict in Yemen, setting off a humanitarian crisis.
The U.N. said last week
that it had verified 828 civilian deaths since the airstrikes began in late March. It also estimated that 450,000 Yemenis have been driven from their homes
by the recent fighting. Thousands of people have fled the country.
The humanitarian pause in recent days has enabled aid groups to address some of the most critical problems facing residents but does nothing to solve the broader crisis.
"Humanitarian assistance cannot replace the needs of 26 million people who have been cut off from a regular supply of commercial imports of food and fuel," said Julien Harneis, a UNICEF representative in Yemen.
During the pause in fighting, huge lines formed at some gas stations in Sanaa, the Yemeni capital, as residents rushed to try to stock up, according to one man, who declined to be identified.
He said the halt in bombings and antiaircraft fire was welcome but that many difficulties remained, notably the shortage of food, electricity and medical supplies.
Some people who could afford it seized the opportunity to board flights out of the country.