DUBAI, Sept 9 (Reuters) - Several merchant vessels in the northern Gulf and Gulf of Oman were hit by disabling fire during military activity in the region overnight, the United Kingdom Maritime Trade Operations agency said on Wednesday.

The British navy-affiliated UKMTO said it was unable to confirm any casualties or environmental impact.

Separately, UKMTO reported another incident on Wednesday, 24 nautical miles from Port Rashid, in the United Arab Emirates. It said a vessel was sighted listing while at anchor, possibly indicating it had taken on water following an attack by an unknown projectile.

On Tuesday, U.S. Central Command forces destroyed five Iranian crude oil tankers following attempted missile attacks on a U.S. Navy warship over the previous two days.

Iran's Revolutionary Guards said on Wednesday they had attacked two U.S. vessels and eight oil tankers in the Gulf in response to the U.S. attack on the Iranian tankers.

The Guards said the 10 vessels had attempted to cross an area of the Strait of Hormuz that they described as "prohibited and unsafe".

(Reporting by Jana Choukeir; Editing by Andrew Heavens and Alex Richardson)