Sri Lanka's government on Tuesday announced a slew of emergency tax increases to help combat a debt crisis that has forced it to seek a bailout from the International Monetary Fund.

Prime Minister Ranil Wickremesinghe said the government would raise value added tax, currently between 8% and 11%, to a flat 15% with immediate effect.

The premier also said he would suspend a planned lowering of corporate taxes for one year and revive a capital gains tax, abolished in 1987, to take effect from this year.

The moves are aimed at repairing a mounting debt crisis that led ratings agency Fitch to downgrade Sri Lanka's credit rating last week.  

In a special statement to parliament, Wickremesinghe blamed the previous government for allowing debt to spiral, saying his ministers had uncovered $7bn in loans unaccounted for in the national budget.  

"We have to overcome the debt trap of the previous regime," Wickremesinghe said.

"The global downturn has reduced room for restructuring this debt," he said.

The IMF sent a mission to review Sri Lanka's economy in February, saying it had warned the authorities they should make a "stronger effort" to immediately reduce the deficit.

The fund later confirmed the island nation had asked for financial assistance, but did not give details on the value of a potential bailout.

President Maithripala Sirisena's government went on a spending spree after taking power in January 2015 to deliver on election promises of higher wages and lower prices.

But the move increased the country's deficit and sparked concern over balance of payments.

The country last month received pledges of over $2bn in loans and equity from the Asian Development Bank over three years.