Hundreds of ships were left unable to move between the Black Sea and the Aegean after Turkey closed the Dardanelles Strait to clear the area for planes fighting nearby forest fires.

Around 300 vessels were waiting to cross the Dardanelles and Bosphorus straits as of Wednesday afternoon, according to Mustafa Can, chairman of Istanbul-based maritime transport company Transbosphor. 

The disruption could start to affect freight rates if the fires in Turkey’s Canakkale province aren’t put out in the next few days, Can said by phone. The Coastal Safety Directorate said the Dardanelles will remain closed until at least Thursday to allow firefighter planes to operate.

North-south traffic was also suspended in the Bosphorus strait that runs through Istanbul, after an oil tanker sailing from Russia to China called Guanyin suffered a mechanical failure near the entrance of the waterway.