Tens of thousands marched on beleaguered Sri Lankan President Gotabaya Rajapaksa's office on Saturday, in the biggest protest to date over the country's dire economic and political crisis.

Sri Lanka's 22 million people have seen weeks of power blackouts and severe shortages of food, fuel and other essentials in the country's worst economic downturn since independence in 1948.

Saturday's social-media organized protest drew the largest numbers since the crisis blew up last month, according to AFP reporters.

Sri Lanka has been facing economic instability recently as a severe shortage of foreign currency has left the government unable to pay for essential imports, including fuel.

Sri Lanka's business community, which largely funded Rajapaksa's election campaign, appeared to ditch the president on Saturday.

"The current political and economic impasse simply cannot continue any further, we need a cabinet and interim government within a week at most," said Rohan Masakorala, head of Sri Lanka Association of Manufacturers and Exporters of Rubber Products.

His association joined 22 other business and industry organizations that are seeking a change of government, saying daily losses had reached around $50 million due to the fuel shortage alone.

In a joint statement, they said that they were responsible for generating nearly a quarter of the country's $80.17 billion gross domestic product and warned millions of jobs would be in jeopardy.

Newly appointed central bank governor Nandalal Weerasinghe said a series of monetary policy blunders had led to the current crisis with no dollars to finance many imports.

In a desperate attempt to shore up the free-falling Sri Lankan rupee, Weerasinghe on Friday implemented the country's biggest-ever interest rate hike of 700 basis points. "We are now in damage control mode," he said.

Weerasinghe added he expected the Sri Lankan rupee to stabilize and dollar inflows to improve as he relaxes his predecessor's tight foreign exchange restrictions which he described as counter-productive.

Sri Lanka's main opposition alliance, Samagi Jana Balawegaya on Friday demanded the government resolve the ongoing economic crisis or face a no-confidence motion.

The government is preparing for bailout negotiations with the International Monetary Fund next week, with Finance Ministry officials saying that sovereign bond-holders and other creditors may have to take a haircut.

New Finance Minister Ali Sabry told parliament on Friday that he expects $3 billion from the IMF to support the island's balance of payments in the next three years.

"We hope to get about a billion dollars a year in the next three years totaling a support of three billion," he said adding that Colombo will also seek a debt moratorium.

(With input from AFP)