SIMIC

The quarantines make it difficult for ships to change crews, contributing to delays in the shipping process that could worsen the supply chain crisis.

China has a zero-Covid policy, imposing stringent containment measures as it tackles its latest wave of outbreaks.

For example, on Halloween night, 30,000 people were locked inside Shanghai Disneyland after just one Covid crisis case was detected.

The latest measure involves a mandatory quarantine of up to seven weeks, around 49 days, for Chinese seafarers returning from overseas.

The quarantine takes place in designated facilities and is paid for by employers.

The nation has also banned crew changes for foreign seafarers, with ships that had their crews changed out elsewhere needing to wait before they can enter Chinese ports.

"China's restrictions cause knock-on effects," said International Chamber of Shipping secretary general Guy Platten.

"Any restrictions to ship operations have an accumulative impact on the supply chain and cause real disruptions." said Mr Platten.