It hardly seems the gateway to a new life of safety and prosperity: An office tucked away in a grey apartment block in Istanbul. Yet every day, dozens of Iraqi Catholics queue here, hoping it will open the door to a new life free of fear.

The Chaldean Catholics, members of Iraq's Assyrian minority, have fled Baghdad and the now jihadist-controlled city of Mosul to escape the violence that has frequently targeted Christians since the US-led invasion of 2003.

The current threat posed by Islamic State (IS) militants who regard Christians as heathens has prompted more to leave and makes a return inconceivable for those who already left.

From Turkey they must deal with the mountain of paperwork to build new lives abroad, possibly with relatives already living in exile.

For help, they flock to the non-descript office of Turkey's own tiny Chaldean community in Istanbul, run by its vicar Francois Yakan, who in 2005 founded the organisation Ka-Der aimed at helping Chaldean refugees in Turkey.

The Chaldean Catholics -- who split with the Orthodox faith followed by much of the world's Assyrian community in the 16th century to follow the pope -- are awaiting the upcoming visit of Pope Francis to Turkey, which begins Friday, with huge anticipation.

- 'No idea where to go' -

On a typical afternoon, dozens of Iraqi Chaldeans wait at the office, many of them with stories of long and complicated years in exile amid the chaos in Iraq.

"I stayed five years in Syria and I have now been in Turkey for a month," said Hanna (not her real name), a mother of five children. "I want to see Pope Francis so he helps me to go to Australia as I want my daughters to do their studies there."

Yakan works personally on every refugee case, helping them register with UNHCR, pay bills or receive urgent food aid.

"The situation of the refugees has become unbearable," he said.

"Their demands for emigration can take years due to the receiver countries and because there are too many requests here in Turkey.

"In general their families who are already abroad are able to help them but they do not have the right to work. So it is very hard."

A husband and wife from Mosul, Faer and Asmaa, bear out his words. Faer has undergone four heart operations already, working up bills that he knows he cannot pay.

"We have been on the road since 2008. First in Lebanon, now here. We have no idea where to go. We just cannot anymore," said Asmaa.

Yakan is working with a Turkish organisation to negotiate a reduction in their hospital bill. "The problem is we cannot help everyone in need," he said.

- 'A sign of hope' -

His budget of just 150,000 euros ($185,000) a year can only be used for urgent situations.

For other expenses, he needs to count on the generosity of the Istanbul Christian community or donations from outside, including the European Union. It is also now increasingly dealing with Syrian refugees as well as Iraqis.

But after almost 10 years of work, his organisation can already claim success, helping some 55,000 Iraqi Chaldean and other refugees move to new lives in other countries.

His success is in stark contrast to the size of Turkey's own Chaldean community, which according to officials numbers only 816.

"When I look at what we have done, I am happy that we dared to create an organisation to save all these people," said Yakan.

"Our role is to protect the faith of all these eastern Christians who are being persecuted because of their beliefs."

He is hoping for a serious impulse from the visit of Pope Francis, who on Saturday afternoon will celebrate Catholic mass in Istanbul at the Cathedral of the Holy Spirit.

"His arrival in Turkey is a good sign for the Christians of the Middle East, especially those who are on the roads of exile. And for the thousands of refugees who we have in Turkey, it is a sign of hope," he said.