The United Arab Emirates says four commercial ships were subjected to "sabotage operations" Sunday near its territorial waters in the Gulf of Oman.
Authorities gave no details, however, on what kind of sabotage they suspect or to whom the ships belong, other than saying they were of different nationalities.
They say no one was hurt and no chemicals or fuel were spilled from the ships.
The UAE did deny Iranian and Lebanese news reports of explosions at the port of Fujairah and added "media outlets must be responsible and rely on official sources."
The UAE says international bodies are helping with the investigation.
"Carrying out acts of sabotage on commercial and civilian vessels and threatening the safety and lives of those aboard is a serious development," the foreign affairs ministry said Sunday, urging all nations to take their responsibilities to prevent actions by anyone looking to undermine maritime safety.
UAE officials declined to say who they thought was behind whatever happened on the ships.
The U.S. Maritime Administration warned last week of what it calls the "increased possibility that Iran and/or its regional proxies could take action against U.S. and partner interests... by targeting commercial vessels, including oil tankers or U.S. military vessels."
There has been no response from Iran. But the head of parliament's national security committee tweeted "security of the south of the Persian Gulf is like glass."