Striking Hong Kong dock workers camped outside the headquarters of Asia's richest man Li Ka-shing pledged to stay put Friday despite the collapse of a contractor at the centre of the dispute.

The workers were demanding a 20 percent pay rise as the strike entered its 23rd day, and called on Li to intervene in the impasse, which has drawn attention to the city's high living costs and wealth gap.

About 150 workers were gathered alongside a dozen tents and makeshift structures outside the Cheung Kong Building in the southern Chinese city's financial district, after marching there Wednesday.

Office workers turned their heads at banners reading: "Richest in Asia, meanest in the world" and "Pay up Li Ka-shing", with many contributing to a strike fund the dockers say has reached HK$5.6 million ($7.2 mn) amid strong public support.

Li's Hongkong International Terminals (HIT) has tried to distance itself from the dispute, saying the workers are not direct employees but were taken on by subcontractors, which set their own levels of pay.

On Thursday, one of the contractors, Global Stevedoring Service Company Ltd, announced that it would have to wind up on June 30 after 130 of its 170 workers went on strike, saying it was unable to continue operating.

But the workers appeared undaunted.

"I hope that brother Shing will speak out on the pay dispute," said Sun, a 45-year-old ship worker who did not want to give his full name, one of up to 400 workers striking throughout the city.

"Once the topic of wage increases comes up, the company won't give any concrete answers," he added, demanding hourly wages increase from HK$50 to HK$60.

Union of Hong Kong Dock Workers general secretary Stanley Ho said he wanted to negotiating directly with HIT rather than the contractors.

"If HIT comes to the negotiating table... the whole situation could be resolved tomorrow," he told a press conference, adding that Global workers were highly experienced and were likely to find work with the other contractors.

Li's vast empire includes supermarkets, pharmacies and housing. HIT, which operates 12 berths, is a unit of Li's Hutchison Whampoa, and controls about 70 percent of the city's port traffic.

The city's housing and transport secretary Wednesday said the strike was delaying some shipments for between one and eight days, and that the port's productivity level was down to as much as 70 percent.

HIT Thursday urged the "parties concerned" to return to the negotiating table, saying Hong Kong faces stiff competition from other regional ports.

"If all parties do not consider the proposals with an open mind and try to understand the challenges that the industry is facing, workers across the entire logistics industry will suffer," it said in a statement.