Three French nationals and one Iraqi working with a French Christian charity in Iraq have been missing since Monday, the group announced Friday.

The four men with SOS Chretiens d'Orient (Christians of the Middle East) went missing near the French embassy in Baghdad, the organisation's director Benjamin Blanchard told a news conference in Paris.

No ransom demand has been received as yet and no group has claimed responsibility for their disappearance, he added.

SOS Chretiens d'Orient has been working with persecuted Christians in Iraq since 2014 when Islamic State jihadists overran the province of Mosul, displacing tens of thousands of minority Christians and Yazidis.

It is principally active in the Iraqi Kurdish capital Arbil, where many Christians sought refuge.

The missing workers were in Baghdad "to renew their visas and register the association with Iraqi authorities," Blanchard said.

They were also due to inspect the group's activities in the city, including the opening of a new school.

They left their hotel by car for a meeting "which posed no problem," Blanchard said, adding that French and Iraqi authorities were working together to try locate them.

However they did not return and the charity sought in vain to contact them on Tuesday before contacting the French authorities early Wednesday.

- Help Christians stay -

The charity's director described the men as "experienced staff members who have been working with us for years" and who had "perfect knowledge of conflict zones".

He declined to give the men's identities.

The French foreign ministry and the French embassy in Iraq refused to comment on their disappearance.

"The French and Iraqi authorities are coordinating today on the enquiry and to retrace their steps," said Blanchard, stressing that he was in "close contact" with the worried families.

Baghdad has been gripped by demonstrations for several months.

The protests initially targeted a government widely seen as corrupt and meddling by neighbouring Iran.

But in recent weeks America's military presence in Iraq has become a hot-button issue since a US drone strike killed Iranian general Qasem Soleimani and a top Iraqi commander in Baghdad on January 3.

SOS Chretiens d'Orient, which is also active in Syria, Lebanon and Egypt, is one of several Western charities working with Christians in the Middle East.

The aim of the group is to "help Christian communities remain (in the region) and rebuild" their lives, Blanchard said.

- Persecution after Saddam fell -

The organisation, which is fiercely critical of Islam, portraying it as a threat to Christianity in the Middle East, drew criticism in the past for sending young French volunteers to Syria and Iraq for months at a time.

Photos regularly published by the non-government organisaiton on Twitter show volunteers visiting Christian families in Arbil and conducting French language classes.

Before the US-led invasion of Iraq in 2003, the number of Christians in Iraq, home to one of the world's oldest Christian populations, ran to an estimated 1.5 million.

After the fall of Iraqi dictator Saddam Hussein they suffered widespread persecution, culminating with the purges carried out by IS in 2014.

By the summer of 2019, their number had fallen to around 250,000, Arbil Archbishop Bashar Warda said during a speech in Britain last year, warning the community was "close to extinction".

Several Western countries including France had nationals kidnapped by armed groups in Syria in 2013 and 2014 but in recent years the situation has eased.

Radio France Internationale said Friday that two of its freelancers were kidnapped briefly last month before being released.

Currently, the only French person confirmed being held hostage anywhere in the world is Sophie Petronin, an elderly charity worker abducted by gunmen in northern Mali in December 2016.

No group claimed responsibility for kidnapping until July 2017, when Al-Qaeda's Mali branch released a video showing her.