Sri Lanka marked 75 years since independence with a sombre military parade on Saturday, as its president urged reflection on past "errors and failures" at a time of national crisis.

Since the 1948 end of British rule, the island nation has spent much of its history at war with itself, including a decades-long Tamil separatist rebellion that claimed up to 100,000 lives and two deadly communist insurgencies.

Its 22 million people are also still reeling from the hardships triggered by an unprecedented economic collapse last year that brought months of food and fuel shortages.

President Ranil Wickremesinghe, who took office last July at the peak of the resulting political unrest, said Saturday's anniversary came at "an extremely critical and challenging time".

"It presents an opportunity for us not only to review our strengths and gains as a nation but also to rectify our errors and failures," he said in a statement.

Wickremesinghe, flanked by top military brass, watched the hour-long procession of soldiers and army vehicles along a seafront promenade in the capital Colombo, inaugurated by ceremonial artillery fire but boycotted by opposition parties.

For several months last year the boulevard was the site of a protest encampment erected by Sri Lankans outraged over the island's economic calamity and mismanagement by its leaders.

The protest movement peaked in July when a huge crowd stormed the home of Wickremesinghe's predecessor and chased him into temporary exile, from where he issued his resignation.

Wickremesinghe ordered security forces to dismantle the camp hours after he was sworn into office and has since set about repairing Sri Lanka's ruined finances.

His government has hiked taxes and is negotiating with international creditors including India and China to clear the way for an urgently needed International Monetary Fund bailout.

"I am confident that even at this juncture we will pool our energies... to rise up from the current economic abyss and build back stronger," Wickremesinghe's statement said.

Troubled history

But the impact of the crisis is still being acutely felt, with Wickremesinghe saying last week that the economy had contracted by up to 11 percent in 2022.

On Friday the UN children's agency reported that nearly one in three Sri Lankans were in need of humanitarian assistance as a result of the downturn.

"Sri Lanka is a bankrupt nation, so we have to start from zero now," political analyst Ranga Kalansooriya told AFP ahead of the independence anniversary.

The economic collapse is the latest of several calamities that have pockmarked Sri Lanka's history since independence.

Nearly 31,000 people were killed when the 2004 Boxing Day tsunami struck the tropical nation's coastline.

A series of coordinated Islamist attacks on hotels and churches during Easter Sunday services in 2019 killed 279 people.

Rights groups say that up to 40,000 civilians were killed in the final weeks of the decades-long civil war during an army assault that crushed the remnants of the Tamil Tigers leadership.

Sri Lanka has resisted international calls for a probe into war crimes allegations and later governments have been accused of abetting continued discrimination against the island's Tamil minority.

Kalansooriya said Sri Lanka had yet to heal the wounds from the long conflict and its political leaders had failed to bring reconciliation.

"We needed a Mandela in Sri Lanka," he said, "but what happened in the aftermath was entirely different."