Kuwait's main oil export port stopped allowing tankers to dock in a thick dust storm on Tuesday, but those already loading at the terminal will be allowed to leave, a Kuwait Oil Tanker Company spokesman said.

"As of 2 am there are no new berthing operations. But whatever vessels that are already berthed have been loading," the spokesman said.

"Once they complete loading they can sail out. These are decisions from the port authorities. New vessels that are arriving will have to wait."

Kuwait is one of the world's leading crude oil exporters, with production running at about 3 million barrels per day.

Traffic at the nearby commercial port of Shuwaikh was also disrupted, its head of marine operations said.

Visibility in Kuwait fell to around 500 metres in the city centre due to the dust storm. – Reuters