A plea for help has been issued from another ship stuck off China thanks to the country's ongoing trade dispute with Australia.

A letter sent from the 179,000-dwt Knightship (built 2010) said that the crew has been at anchor off Jingtang on the Seanergy Maritime Holdings-owned, Liberian-flagged capesize bulker for five months with no end in sight.

"The crew on board are like political hostages and slaves owned by charter and cargo owners," said the letter to TradeWinds that was purportedly issued on behalf of the crew.

"This is a violation of human rights. We are humans and have rights for our freedom.

"[We] have fully expired contracts, mental health in critical stance, our families without us [for] more than one year."

The ship's owner and master, however, have both claimed that the letter was not issued by the vessel's entire crew but instead represented the view of a single seafarer.

The Knightship is one of approximately 50 idled bulkers that are collectively laden with more than $500m-worth of Australian coal, according to Bloomberg. The ships are reportedly prevented from discharging as Beijing clamps down on imports from Australia.

Australia-China relations, already strained after Australia blocked Huawei Technologies from building its 5G mobile network, soured further when Australia requested an inquiry into the origin of the Covid-19 outbreak in Wuhan last year.

In response, China put restrictions on various Australian imports and, this autumn, reports surfaced that the bans included coal.

Chinese foreign ministry spokesman Zhao Lijian reportedly said the country's customs agents have done inspections of Australian coal and have found "many instances where the cargoes failed to meet environmental standards".

According to the letter, the ship is chartered by commodities trading giant Glencore, which declined to comment.

Seanergy Maritime Holdings Corp chief executive Stamatis Tsantanis said only that the Knightship was on charter to a "prominent global charterer" and that crew changes are not allowed in the area.

He added that the ship might be able to berth in mid-January.

"We are in constant discussions and cooperation with our charterers and our P&I [protection and indemnity club]," Tsantanis said.

"However, our top priority is the health and well-being of the crew onboard, and we spare no effort or expense to improve the quality of life as much as possible."

Stamatis Tsantanis, chief executive of Seanergy Maritime Holdings Corp. Photo: Seanergy Maritime Holdings Corp

The Knightship's master has issued a letter of his own, provided to TradeWinds by Seanergy, echoing the company's message, including that the ship's crew is receiving double pay.

"Owners are performing the bet possible efforts to improve our living conditions onboard, either financially and with extra recreation features or with mental and health support," the master wrote.

He said the crew of the master and crew of the ship had no involvement in the complaints made on social media about the vessel's information.

The master, whose name is not legible, wrote that the letter calling for help for the crew involved "a single isolated case" for which the ship's owner has received support from its protection and indemnity club and the Mission to Seafarers.

TradeWinds has requested to interview the master.

The letter calling for help blamed Glencore and the unnamed cargo owner for keeping crew on board, arguing that Chinese port authorities would allow the ship to leave the anchorage for a crew change, but the charterer and cargo interests "don’t want to spend money".

It came two weeks after the National Union of Seafarers of India complained that crew on the 179,300-dwt Jag Anand (built 2011) were effectively on board a "floating prison".

The union said 15 of the Jag Anand's crew have served for at least 16 months and the rest for 13 months.

The letter purporting to come from the Knightship's crew said seafarers on other ships in the anchorage had been on board for as long as 20 months.

"People have to stay on board [an] unknown duration of time and wait until the vessel is finally discharged," the letter said.

"People cannot wait anymore and cannot keep silent. We are not slaves and hostages!"

Eric Martin contributed to this story