The board of China Shipping Container Lines (CSCL) has announced a proposal to bareboat up to eleven units of 21,000 TEU ultra-large containerships via its subsidiary China Shipping Nauticgreen Holdings.

According to a filing to the Hong Kong Stock Exchange, the Chinese shipowner said the plan is to bareboat charter six of the mega-sized vessels with options for five more similar ships.

CSCL will decide on the options for five more vessels, which can be ordered for construction by its subsidiary, China Shipping Nauticgreen Holdings, within six months of the charter agreement being signed.

The six firm vessels are already on order. If the five optional vessels are exercised, they will be chartered under the same terms as the six firm vessels, according to media reports.

No details were provided on the duration or financial terms of the charters, nor was the vessel owner from whom the unidentified boxships will be bareboated.

The decision to bareboat in the boxships was made to "uphold the low-carbon environmental protection concept of operations, comply with the current developing trend of the large-scale shipping market, and to further optimise the fleet structure of the group", the filing said.

CSCL said it would provide more information on the prospective deal after the charter agreement had been signed.