ANKARA: Pope Francis on Tuesday arrived in Turkey for his first visit to the overwhelmingly Muslim but officially secular state, in a challenging trip aimed at building bridges with Islam and supporting the embattled Christian minorities of the Middle East.

The pope is spending the first of three days in Turkey in the capital Ankara, notably holding a meeting with President Recep Tayyip Erdogan at his newly-constructed and hugely controversial presidential palace.

Wearing a long white coat to protect himself against the bitter early winter Anatolian wind, the pope was welcomed to Turkey at Ankara airport by Foreign Minister Mevlut Cavusoglu.

The 77-year-old Argentine pope will move to Istanbul on Saturday and Sunday, visiting key sites of the city's Byzantine and Ottoman heritage as well as meeting the Orthodox Ecumenical Patriarch Bartholomew I.

The trip appears less controversial than the last by a pontiff to mainly Muslim Turkey, the visit by Pope Francis' predecessor Benedict XVI in 2006 which was overshadowed by remarks he had previously made deemed to be anti-Islamic.

But the security of the pope will be paramount for the Turkish authorities.

The close contact with crowds that have been such a feature of the past trips by the charismatic head of the Roman Catholic Church are not expected to feature in Turkey.

Some 2,700 police are set to supervise his visit in Ankara, a number that will rise to 7,000 in Istanbul.

There have also been calls on the pope not to meet Erdogan at his vast presidential palace which has 1,000 rooms, costing no less than $615 million (500 million euros) and seen by critics as an authoritarian extravagance.

But the Vatican has refused to be drawn into the polemic, saying it is merely accepting the invitation by the hosts for the pope, who will be by far the most important visitor so far at the palace.

Erdogan has long been accused by opponents of seeking to erode Turkey's secular foundations with creeping Islamisation. But he also presents himself as a friend of the country's extremely small but varied non-Muslim minorities.

To pray or meditate?

A subject of keen attention will be the pope's visit in Istanbul Saturday to the Hagia Sophia, the great Byzantine church that was turned into a mosque after the conquest of Constantinople in 1453 and now serves as a museum.

His every gesture will be scrutinised later in the day when he visits the Sultan Ahmet mosque, known as the Blue Mosque, one of the greatest masterpieces of Ottoman architecture.

When Benedict XVI visited the mosque in 2006, he assumed the Muslim attitude of prayer and turned towards Mecca in what many saw as a stunning gesture of reconciliation.

The Vatican later made clear he had not actually prayed in the mosque but was “in meditation” and Pope Francis could make a similar gesture.

The visit has hardly sparked waves of enthusiasm in Turkey, where the relatively muted reaction is likely to contrast with the jubilant scenes seen on trips to majority Catholic countries like Brazil.

Previous papal trips to Turkey have been greeted by moaning about the additional traffic congestion in Istanbul's already clogged streets.

Turkey's own Christian community is tiny, just 80,000 in a country of some 75 million Muslims, but also extremely mixed, consisting of Armenians, Greek Orthodox, Franco-Levantines, Syriac Orthodox and Chaldeans.

While only the Chaldeans and Levantines follow the pope in any numbers, Francis is expected to raise his concern about the plight of Christian communities throughout the Middle East amid the rise of Islamic State (IS) militants.

In his talks with Bartholomew I, the “first among equals” of the world's estimated 300 million Orthodox believers, Francis will seek to narrow the schism between the two Churches that dates back to 1054.

Beyond the stepped-up security presence, there has been scant evidence of the pope even coming to Turkey, although banners have been hung on churches with the faces of Francis and Bartholomew and the slogan “welcome!”.

Papal visits to Turkey are still a rarity, Francis will be just the fourth pope to visit the country after Benedict in 2006, John Paul II in 1979 and Paul VI in 1967.