Pope Francis landed in war-battered Iraq Friday on a first-ever papal visit, defying security fears and the pandemic to comfort one of the world's oldest and most persecuted Christian communities.

The 84-year-old, who said he was travelling to Iraq as a "pilgrim of peace", will also reach out to Shiite Muslims when he meets Iraq's top cleric, Grand Ayatollah Ali Sistani.

The pope left Rome early Friday for the four-day trip, his first abroad since the onset of the Covid-19 pandemic, which left the leader of the world's 1.3 billion Catholics saying he felt "caged" inside the Vatican.

"I'm happy to resume travel, and this symbolic trip is also a duty to a land that has been martyred for years," he told journalists aboard his plane.

His plane landed at 1:55 pm (1055 GMT), waving the flags of both Vatican City and Iraq as it taxied on the tarmac at Baghdad International Airport, where Prime Minister Mustafa al-Kadhemi greeted him.

"With love and peace, Iraq's people and government are welcoming His Holiness Pope Francis and reaffirming the depths of this humanitarian bond," Kadhemi said ahead of the pope's arrival.

While Francis has been vaccinated, Iraq has been gripped by a second wave of infection with 5,000 plus new cases a day, prompting authorities to impose a full lockdown during the pontiff's visit.

"I'll try to follow directions and not shake hands with everyone, but I don't want to stay too far," Francis said ahead of his arrival.

- 'We have suffered so much' -

Security will be tight in Iraq, which has endured years of war and insurgency, is still hunting for Islamic State sleeper cells and just days ago saw a barrage of rockets plough into a military base.

Foreign ministry spokesman Ahmad al-Sahhaf said Iraqi authorities had imposed tight security "over the land and air" to ensure the visit goes smoothly.

Francis will preside over a half dozen services in ravaged churches, refurbished stadiums and remote desert locations, where attendance will be limited to allow for social distancing.

Inside the country, he will travel more than 1,400 kilometres (870 miles) by plane and helicopter, flying over areas where security forces are still battling IS remnants.

For shorter trips, Francis will take an armoured car on freshly paved roads that will be lined with flowers and posters welcoming the leader known here as "Baba Al-Vatican".

The pope's visit has deeply touched Iraq's Christians, whose numbers have collapsed over years of persecution and sectarian violence, from 1.5 million in 2003 to fewer than 400,000 today.

"We're hoping the pope will explain to the government that it needs to help its people," a Christian from northern Iraq, Saad al-Rassam, told AFP. "We have suffered so much, we need the support."

- 'We left everything' -

The first day of the pope's ambitious itinerary will see him meet government officials and clerics in the capital Baghdad, including at the Our Lady of Salvation church, where a jihadist attack left dozens dead in 2010.

He will also visit the northern province of Nineveh, where in 2014 IS jihadists forced minorities to flee, convert to Islam or be put to death.

"People had only a few minutes to decide if they wanted to leave or be decapitated," recalled Karam Qacha, a Chaldean Catholic priest in Nineveh.

"We left everything -- except our faith."

Some 100,000 people, around half of the province's Christians, fled -- of whom just 36,000 have returned, according to Catholic charity "Aid to the Church in Need".

A third of returnees want to leave permanently, dismayed by Iraq's rampant corruption, persecution and poverty, which now affects 40 percent of the population.

The exodus is a loss for all of Iraq, said Cardinal Leonardo Sandri, who heads the Vatican's Congregation for the Oriental Churches and will accompany the pope to Iraq.

"A Middle East without Christians is like trying to make bread with flour, but no yeast or salt," he said.

The visit aims not only to encourage Christians to stay in their homeland, but even prompt some emigres to return, from nearby Lebanon or Jordan, or from the far-flung diaspora in countries like Canada or Australia.

In a video address ahead of the trip, Francis evoked "the wounds of loved ones left behind and homes abandoned".

"I come as a pilgrim, a penitent pilgrim to implore forgiveness and reconciliation from the Lord after years of war and terrorism."

- 'Minarets and church bells' -

The pope has insisted on going ahead with the visit despite resurgent violence, including rocket attacks that have left three people dead in recent weeks.

On the eve of Francis's arrival, one shadowy group that claimed a recent rocket attack said it would "halt all military activity" during his visit.

The pope's determination to travel to areas long shunned by foreign dignitaries has impressed many in Iraq -- as has his planned meeting with Sistani, 90, the top authority for Iraq's Shiites.

A highly reclusive figure who rarely accepts visitors, Sistani will make an exception to host Francis at his humble home in the shrine city of Najaf on Saturday.

Banners all over Najaf have celebrated "the historic encounter, between the minarets and the church bells".

Francis, a major supporter of inter-religious dialogue, will afterwards hold an interfaith service at the desert site of the ancient city of Ur, where Abraham is thought to have been born.