UNITED NATIONS - The United Nations condemns the cross-border attacks by the Houthis in Yemen against multiple sites in southern Saudi Arabia, which affected civilian and energy infrastructure, said a UN spokesperson on Tuesday.

The world body also expresses deep concern over reports of civilian casualties in the attacks, said Stephane Dujarric, spokesperson for UN Secretary-General Antonio Guterres.

The United Nations is equally concerned by the intensification of military clashes across multiple front lines within Yemen, particularly reports of possible civilian casualties resulting from the fighting, said the spokesperson.

"We call upon the parties to exercise restraint and prevent further escalation, and further urge them to uphold their obligations under international humanitarian law to refrain from directing attacks against civilians or civilian infrastructure, and to take constant care to spare the civilian population, civilians, as well as civilian objects," Dujarric said.

UN Special Envoy for Yemen Hans Grundberg continues engaging directly with the parties with the aim of containing the current escalation and preserving space for dialogue. Continued military escalation risks devastating political, economic and security ramifications for Yemen. The parties should engage constructively with UN-led political efforts, said the spokesperson.