"Israeli airstrikes today on Sana’a International Airport, the Red Sea ports and power stations in Yemen are especially alarming," Stephanie Tremblay told reporters.
The airstrikes reportedly killed at least three people and left dozens injured, Tremblay said.
Her remarks came after Israel struck the airport as World Health Organization (WHO) Director-General Tedros Adhanom Ghebreyesus was about to board a flight. Tedros and his team were unharmed.
The WHO chief was in Yemen to negotiate the release of UN staffers who have been held hostage by the Houthi group for several months and assess the health and humanitarian situation in the war-torn country.
"The Secretary-General remains deeply concerned about the risk of further escalation in the region and reiterates his call for all parties concerned to cease all military actions and exercise utmost restraint," Tremblay said.
Guterres also warned that airstrikes on Yemen’s Red Sea ports and Sana’a airport pose "grave risks" to humanitarian operations at a time when millions of people are in need of life-saving assistance, she added.