The Norwegian Maritime Authority (NMA) has raised the security level for its ships following the attack on tankers at Fujairah in the UAE.
At least four vessels were targeted in what appeared to be a mine attack on Sunday, including two from Saudi Arabia and Norwegian manager Thome's 47,000-dwt Andrea Victory (built 2005).
No one has yet admitted responsibility.
"The security level has been increased because we do not know exactly what has happened," NMA said.
