Residents say that air strikes by Saudi-led coalition hit capital of Yemen on Saturday two hours after a United Nations humanitarian truce began on Friday midnight.
The UN had announced on Thursday an “unconditional humanitarian ceasefire” in Yemen to start on Friday midnight and last until the end of the Islamic holy month of Ramadan.
The air strikes caused big explosions, say the residents.
Saudi-led air strikes, targeting the Iranian-backed Houthis, have killed more than 3,000 people in the conflict-torn Yemen since March.
The UN declared on Tuesday that there were at least 1,528 civilians among the 3,000 dead.
The conflict has caused displacement of another 1 million Yemeni civilians since the air war began.
Nearly half of the country's regions have been facing a food crisis and more than 80 percent of Yemen’s population has been in need of humanitarian aid, with 13 million facing food shortages.
The truce was aimed to allow charities to deliver aid to the 21 million people who are in need of humanitarian aid.
According to the UN, 9.4 million people have been suffering a lack of water.
The Houthis seized the capital Sanaa in September 2014, driving the president Abd Rabbuh Mansur Hadi out of Yemen to the Saudi capital, Riyadh.
Saudi Arabia and its Gulf allies started an aerial operation, dubbed “Decisive Storm” on March 26 to halt the Houthi advancement from Sanaa to Aden as they justified their involvement with the claim of “defending the legitimate government” of Hadi.