UNITED NATIONS, May 8 (Xinhua) -- UN Secretary-General Antonio Guterres urges all sides to exercise maximum restraint to avoid further escalation following the exchange of fire in the Strait of Hormuz, a UN spokesman said Friday.

The secretary-general is concerned by the reported recent exchange of fire in the Strait of Hormuz, Farhan Haq, deputy spokesman for the UN chief, said at a daily briefing.

The secretary-general calls on all parties to fully abide by the ceasefire and refrain from any actions that could lead to renewed escalation or undermine ongoing diplomatic efforts, he said.

U.S. and Iranian forces traded fire on Thursday. The U.S. military said it was a "self-defense" action while Tehran accused Washington of violating a ceasefire that took effect on April 8. ■