Heavy fighting in Yemen between pro-government forces and Shi'ite rebels has killed more than 150 people in the last four days, Yemeni officials and witnesses said Sunday.
Government forces have been trying to seize rebel-held areas along the western coast, while an allied Saudi-led coalition has been targeting the rebels with airstrikes in the northwestern Saada province, a rebel stronghold.
The offensive is being waged by ground troops carrying sophisticated weapons, including shoulder-fired missiles, with air cover from the coalition, the officials said.
Security officials say a Saudi-led airstrike near a gas station in the capital, Sana'a, killed four civilians on Saturday and wounded 10.
The officials spoke on condition of anonymity because they were not authorized to brief the media, while the witnesses did so for fear of reprisals.
In March, an international rights group said fighting along Yemen's west coast has displaced 100,000 people in recent months, mostly from the Red Sea port city of Hodeida. Amnesty International warned that the "the worst could be yet to come."
The port is a vital lifeline from which most of the Yemeni population's food and medicine comes. The coalition accuses the Houthis of using Hodeida and other ports to receive weapons and ammunition from Iran, which denies arming the rebels.
Yemen has been embroiled in a civil war pitting the coalition against the Iran-backed Houthis since March 2015. The coalition aims to restore the government of self-exiled President Abed Rabbo Mansour Hadi.
The three-year stalemated war has killed more than 10,000 people and displaced more than 3 million. It has also damaged Yemen's infrastructure, crippled its health system and pushed it to the brink of famine.
The U.N. considers Yemen to be the world's worst humanitarian crisis, with more than 22.2 million people in need of assistance. Malnutrition, cholera and other diseases have killed or sickened thousands of civilians over the years.