Taiwanese line Yang Ming has declared an option to charter four more 11,000-teu boxship newbuildings from Shoei Kisen of Japan.
The company said it would sign long-term deals for the vessels.
The price per ship is between $100m and $125m, it added, with the total charter cost coming in at between $400m and $500m.
In July, the owner signed charter contracts for five 12,000-teu neo-panamax containership newbuildings with Costamare of Greece and for five vessels of 11,000 teu with Shoei Kisen.