SHANGHAI, April 8 (Reuters) - Bankers and traders are hunkering down in offices in Shanghai, sleeping on camping beds and living off instant noodles or boxed meals to keep China's financial centre running amid a longer-than-expected lockdown against COVID-19.

While the wheels of Shanghai's financial markets are mostly still turning, there are signs that the city's extended lockdown is causing some interruptions, including the suspension of some stock market listing plans, and yuan trading volume falling to more than two-year lows.

Employees bedding down in offices were given air mattresses, pillows and blankets, and were relying on limited facilities. "Colleagues have to share a shabby shower room in the building," a foreign banker who declined to be named said.

Since March 28, an estimated 20,000 financial professionals and other workers have shut themselves in office towers in Shanghai's Lujiazui district, after the city started a lockdown for virus testing.

The strict movement curbs on residents in Shanghai's east, supposed to only last for four days, were later extended city-wide, with no end in sight.

For Shanghai's state-dominated financial sector, ensuring business continuity during the lockdown is an objective it cannot afford to miss.

Bank of Communications Chairman Ren Deqi urged employees at an internal meeting on Tuesday to avoid business shutdowns, likening the political mandate to a "military order".

Camping beds and tents were set up in offices and meeting rooms to allow overnight stays by staff on duty, according to photos shared by the lender, China's fifth-biggest.

State-owned brokerage Haitong Securities Co said its Chairman Zhou Jie had opted to stay with 150 key staff in their offices to help ensure smooth operations. The company urged its staff who were Communist Party members to "charge ahead" in the fight against the virus.

FINANCIAL INFRASTRUCTURE

Shanghai on Friday announced a record 21,000 new cases and a third consecutive day of COVID-19 testing for its 26 million residents.

The city's key financial infrastructure operators, including forex centre Foreign Exchange Trade System, bank card processor China UnionPay, and the Shanghai clearing house, have all unveiled contingency measures to keep businesses running.

Shanghai is also home to numerous brokerages and asset managers, and the city processed around 2,500 trillion yuan ($393 trillion) of financial transactions last year.

Hedge fund manager Shen Yi said he and several employees had to stay in the office during the lockdown to ensure smooth trading and regulatory compliance, with a focus on risk management.

The city-wide lockdown restricted access to the back-up office of his firm, Shanghai Shenyi Investment Co, so he was considering setting up a new office outside Shanghai, said the former Goldman Sachs trader.

Yet bankers and traders said access to food and other essentials such as bottled water had not been an issue, as companies and local government had prioritised supplying them, helping avoid the shortages affecting many other residents.

Shen said a caterer sends boxed rice lunches every day. "We just eat a bit more simply," he said.

It is a scenario that some traders who were working from home - and having to figure out their own meals - said they were starting to envy.

"To be honest, I am rather worried about getting food and vegetables these days, not work," said one such trader who declined to be named.

($1 = 6.3637 Chinese yuan renminbi) (Reporting by Winni Zhou and Brenda Goh; Additional reporting by Samuel Shen; Editing by David Holmes)