Hodeidah, a vital entry point for the UN and other humanitarian aid, has become the center of the conflict in Yemen between the US-backed Arab allies, led by Saudi Arabia and Houthi rebels supported by the ;Iran.
"The increase in violence is one of the most fierce fighting we have seen in months and months," the UN humanitarian coordinator in Yemen, Lise Grande, told CNN.
The Saudi-led coalition said Monday that it had made significant gains in the battle to capture Hodeidah from the Houthi.
A Houthi leader said the latest military escalation of the Saudi-led coalition is in line with an "American vision".
"Based on the experience of the past, we know that this is an American style, invoke peace as they prepare for a new military aggression," Abdul Malik al-Houthi said in a speech broadcast by TV pro-Houthi al-Masirah .
"Saudi aggression depends mainly on military supervision, planning, weapons and US logistical support," he added.
Children at risk, says UNICEF
Humanitarian workers fear that more than 100 civilians may have died in the past week in Hodeidah, CNN has learned.
UNICEF, the UN agency for children, warned on Tuesday that intense fighting in Hodeidah has put the children in the city's hospital in grave danger.
The lives of 59 children are at risk, he said, including 25 who are in the intensive care unit at the al-Thawra hospital in the city.
Hodeidah and neighboring governments represent 40% of 400,000 children in the country suffering from severe acute malnutrition, UNICEF said. "Some of the sickest are taken to hospital for urgent care," he added.
Meanwhile, up to 80% of Yemen's humanitarian supplies, fuel and commercial goods are delivered through the port of Hodeidah, around which the fighting is said to have intensified, the agency said.
"The balance of lives could be catastrophic if the port is damaged, destroyed or blocked," he warned.
The three-year conflict between the US-led Saudi-led coalition and the Iranian aligned Houthi devastated Yemen and reportedly killed at least 10,000 people.
Air strikes intensify
The Saudi-led coalition had launched 400 airstrikes in Hodeidah in recent days, a Yemeni journalist near Houthis told CNN on Wednesday.
"The coalition is using Kilo 16 – a road connecting the capital, Sanaa and Hodeidah – as a battlefield," Hussain Albukhaiti told CNN by telephone. "The coalition distributed leaflets two months ago, warning people and their cars to keep clear of that road."
The US military provides the Saudi coalition with training aimed at minimizing civilian casualties and air supply of coalition warplanes.
The situation in Yemen is "an unprecedented human tragedy", said Tuesday the head of the United Nations Food and Agriculture Organization, José Graziano da Silva.
Mohammed Tawfeeq and Jomana Karadsheh from CNN contributed to this report.