DUBAI (REUTERS) - Four blasts were heard in Yemen's main port city of Hodeida late on Tuesday (Dec 18) on the first day of a ceasefire agreed between the Iran-aligned Houthi movement and the Saudi-backed government at United Nations-led peace talks last week, residents said.

One resident told Reuters the blasts sounded like artillery shelling on the eastern and southern outskirts of the Red Sea port city, vital for food and aid supplies to Yemen.

Other residents said they heard similar explosions.

It was not immediately clear which side was responsible.

Houthi-run al-Masirah TV accused Saudi-led coalition forces of breaking the truce. A coalition spokesman was not immediately available to confirm whether there was a resumption in fighting.

Fighting persisted before coming to a halt when the truce went into effect at midnight on Monday (5am on Tuesday, Singapore time), but Hodeida had been calm throughout the day on Tuesday.

The Houthi group and the government of Abd-Rabbu Mansour Hadi had agreed to cease fighting in the Houthi-held city and withdraw forces amid Western pressure to the end the nearly four-year conflict that has killed tens of thousands of people and left millions of Yemenis threatened by starvation.

The UN, which led the peace talks in Sweden, is trying to avert a full-scale assault on Hodeida after the coalition launched an offensive this year to try to seize the seaport that handles the bulk of Yemen's commercial goods and aid supplies.

The Western-backed Sunni Muslim Arab coalition led by Saudi Arabia and the United Arab Emirates intervened in the civil war in 2015 against the Houthis to restore Mr Hadi's government, which was ousted from the capital Sanaa in 2014.