The war between the Shiite Houthi rebels and troops loyal to President Abedrabbo Mansour Hadi escalated in 2015, when he fled into Saudi exile and the Saudi-led military coalition intervened
The battleground Yemeni port city of Hodeidahh was calm Thursday after a minor exchange of fire between the warring parties overnight, a pro-government official said.
Military officials and residents have said that there has been intermittent fighting between loyalists -- backed by a Saudi-led coalition -- and the Iran-aligned Houthis since a truce in the lifeline Red Sea port city and its surroundings came into force on Tuesday.
A pro-government official told AFP that four loyalists were wounded on Wednesday night.
"The exchange of fire lasted for about half an hour, and there is uneasy calm this morning," he said.
The official added there has been intermittent fighting on a number of battlefronts in Hodeidah province, including the districts of Hays and Al-Tuhayta.
The pro-government forces and the Houthi rebels exchanged accusations on Thursday that the other side was violating the ceasefire agreement reached at talks in Sweden earlier this month.
UN observers are due in Yemen to head up monitoring teams made up of government and rebel representatives tasked with overseeing the implementation of the UN-brokered ceasefire, under the auspices of a Redeployment Coordination Committee.
The UN chair of that committee, Patrick Cammaert, convened its first meeting by videoconference from New York on Wednesday "to discuss the general outlines of its work, including agreement of a code of conduct", UN spokesman Stephane Dujarric said.
UN chief Antonio Guterres was "breathing down the neck" of officials to make sure the UN observers are deployed as soon as possible, Dujarric said.
He added that Cammaert will head on Thursday to Jordan's capital Amman, from where he will travel to the Yemeni capital Sanaa and Hodeidah.
Brigadier Ahmed Al-Kokbani, a Yemeni government representative on the committee, told AFP that the observers' meeting with Cammaert covered the bases of the committee's work.
"Cammaert asked members of the team to work diligently in calming the situation and to reject any violations (of the truce deal)," he said.
The Saudi-led coalition warned Wednesday that the hard-won ceasefire agreement will collapse if rebel violations persist and the United Nations does not intervene.
The Redeployment Coordination Committee's observers are due to oversee the withdrawal of the warring parties from Hodeidah, including a rebel pullout from the city's docks that are the point of entry for 80 percent of Yemeni imports and nearly all UN-supervised humanitarian aid.
The committee chair is expected to report to the Security Council on a weekly basis as part of a major diplomatic push that is seen as the best chance yet to end the four-year conflict.
The war between the Shiite Houthi rebels and troops loyal to President Abedrabbo Mansour Hadi escalated in 2015, when he fled into Saudi exile and the Saudi-led military coalition intervened.
Since then, the war has killed some 10,000 people, according to the World Health Organization, although human rights groups say the real death toll could be five times as high.