Sri Lanka's new government declined to sing the national anthem in Tamil, the country's second national language, during the island's Independence Day celebrations on Tuesday.

This was a departure from the previous government which sang the anthem in the country's two primary languages to promote ethnic harmony in the aftermath of a decades-long civil war.

Sri Lankan President Gotabaya Rajapaksa was elected last year largely with votes of majority Buddhist Sinhalese. Minority Tamils overwhelmingly voted against him.

Rajapaksa was a top defence official in the civil war and played a major role in defeating the rebel Tamil Tigers. Many ethnic Tamil civilians were killed or went missing in the war.

The country's 72nd anniversary of independence from Britain was celebrated in Colombo with military parades and air shows.

Rajapaksa said in his speech that he is the president of all communities, reiterating a sentiment he made in his elections speech.

"I have the vision that I must serve as the leader of the country looking after all citizens rather than serve as a political leader concerned only about a particular community,” he said.

"As the president [...] I represent the entire nation irrespective of ethnicity, religion, party affiliation or other differences,” Rajapaksa said.

Rajapaksa supporters opposed singing the national anthem in the Tamil language during the previous administration.

Tamil politicians had requested Rajapaksa to continue the practice of singing the Tamil translation of the national anthem recognised by the constitution in order to give the Tamil community a sense of belonging to the country after decades of estrangement with the state.

At a separate location a group of civil activists from both Sinhala and Tamil communities sang both versions of the anthem in a show of support of the Tamils.

Tamil Tiger rebels fought a 26-year civil war to create an independent state for ethnic Tamils, complaining of systemic marginalisation by the Sinhalese majority-controlled state since independence.

Sri Lankan troops defeated the rebels in 2009 with Rajapaksa playing a key role as a defence bureaucrat in the government led by his brother, former president Mahinda Rajapaksa.

According to conservative United Nations estimates, about 100,000 people were killed in the civil war.

Both the government and the rebels were accused of committing serious human rights violations.