UN Special Envoy to Yemen Hans Grundberg on Sunday voiced his grave concern over recent U.S. airstrikes in and around the Ras Isa fuel port northwest of Yemen's Red Sea city of Hodeidah.

"Echoing the (UN) Secretary-General (Antonio Guterres), I am gravely concerned about the impact of the U.S. airstrikes in and around Ras Isa port on civilians, particularly truck drivers and port workers, as well as on civilian infrastructure," Grundberg wrote on social media platform X.

The cycle of attacks on the Red Sea by Houthis and the United States "jeopardizes peace efforts and risks drawing Yemen further into the regional conflict," he wrote, urging restraint, de-escalation, and protection of civilians and civilian infrastructure by all sides in accordance with international law.

Attacks on the Red Sea must stop with "credible guarantees" that protect it from "becoming a prolonged arena of conflict," which are "essential" for keeping Yemen "from sliding further away from peace" and for global security, he wrote.

In the deadliest raid since the renewed U.S. airstrikes in mid-March, the U.S. army launched a series of attacks on Thursday night targeting and destroying the Houthi-controlled Ras Isa fuel port and concrete tanks storing imported fuel. According to an update from Houthi-run health authorities early Saturday, at least 80 people were killed and 150 others wounded.

Among the casualties were port workers and five paramedics, who were reportedly killed in a second wave of airstrikes while arriving on ambulances to assist the wounded.

Early Saturday, Mohammed Ali al-Houthi, head of the Houthi Revolutionary Committee, vowed to retaliate against the renewed U.S. airstrikes. The group said later in the day that it shot down two U.S.-made MQ-9 drones in 24 hours.