A Tamil-language version of Sri Lanka's national anthem has been sung at the country's independence ceremony, lifting an unofficial ban in another step toward post-civil war ethnic reconciliation.

School children sang the national anthem in Sinhalese, from the ethnic majority group, and the minority Tamil language at the 68th anniversary of independence from Britain on Thursday.

The move, despite opposition from nationalists, is seen an effort to reach out to the Tamils who fought a nearly 26-year civil war for an independent state. The civil war ended in 2009.

President Maithripala Sirisena says he will unite the nation, a process which has not been given prominence since independence.

Sirisena's hardline predecessor Mahinda Rajapaksa had imposed an unofficial ban on the Tamil version of the national anthem.