Pope Francis has used his first visit to Sri Lanka to call on the country to uncover the truth of what happened during its civil war, as part of a healing process between religious communities.

He is the first Pope to visit Sri Lanka since the war between troops and Tamil separatists ended in 2009.

Soon after landing in Colombo, the pontiff appeared to make the case for a truth commission to investigate the 26-year-long civil war, an election pledge of the government voted into office last week.

"The process of healing also needs to include the pursuit of truth, not for the sake of opening old wounds, but rather as a necessary means of promoting justice, healing and unity," he said, wearing a long garland of yellow and white flowers.

A 2011 UN estimate put the death toll from the final army assault in the war at up to 40,000 civilians.

The Pope called for a more inclusive society in Sri Lanka, in comments that seemed directed at former president and wartime leader Mahinda Rajapaksa, who lost office after a resurgence in religious tensions.

"The great work of rebuilding must embrace improving infrastructures and meeting material needs but also, and even more importantly, promoting human dignity, respect for human rights, and the full inclusion of each member of society," he said.

"All members of society must work together; all must have a voice."

Mr Rajapaksa is feted as a hero for ending three decades of war and presiding over a period of fast economic growth and infrastructure reconstruction.

However, he refused to allow a fully independent inquiry into alleged war crimes and presided over a period of growing repression of religious minorities as well as political opponents.

His rule coincided with isolated attacks led by hardline Buddhist monks against churches and other Christian centres.

The Pope was greeted at the airport by president Maithripala Sirisena, who said the papal visit was a blessing for his new government.

Traditional Sri Lankan dancers and drummers lined the red carpet, along with around 50 costumed elephants.

Independent domestic inquiry

Mr Sirisena, who took office only days ago, has promised an independent domestic inquiry into the allegations of wartime rights abuses under his predecessor.

His new prime minister Ranil Wickremesinghe said before the election his government would also ensure a South African-style truth commission.

Only around six per cent of Sri Lanka's 20 million-strong population is Catholic, but the religion is seen as a unifying force because it includes people from both the majority Sinhalese and minority Tamil ethnic groups.

Mr Sirisena pledged to protect religious freedoms and promote a new culture of tolerance on the island.

"My government is promoting peace and friendship among our people after overcoming a cruel terrorist conflict," he said.

"We have people who believe in religious tolerance and coexistence based on centuries-old religious heritage."

About 70 per cent of Sri Lankans are Buddhists. Hindus make up about 13 per cent and Muslims 10 per cent.

Catholics are about seven per cent, split between ethnic Sinhalese and Tamils.

Sri Lanka's first saint

On Wednesday, which has been declared a national holiday, the Pope will hold a mass on the Colombo seafront and canonise Sri Lanka's first saint, 17th century missionary Fr Joseph Vaz.

He was a Catholic priest credited with rebuilding the Church in Sri Lanka in the 17th and 18th centuries, after Dutch occupiers imposed Calvinism as the official religion.

He will also visit a small church in the jungle that was on the front lines of the ethnic conflict, which killed around 100,000 people.

The Our Lady of Madhu church in the mainly-Tamil north provided sanctuary during the fighting, and is now a pilgrimage destination for Christians from across the ethnic divide.

After two days in Sri Lanka, the Pope will visit the Philippines, a bastion of Christianity in the region, where he is set to attract one of the biggest-ever gatherings for a head of the Catholic Church.

Reuters/AFP