ROME (AFP) - The Vatican has given US$40,000 (S$50,000) in emergency aid to Christians in Iraq displaced by a jihadist onslaught, religious news agency imedia said on Friday.

Most of the money will go to help those from the northern city of Mosul, where Islamic State insurgents last week ordered the hundreds of Christian families to convert to Islam, pay tribute, or leave the city, prompting thousands to flee.

Christians and other minorities who failed to comply were threatened with execution, while the property of those who left the city was forfeited to the Islamic State.

The agency said it was "a first gift for persecuted Christians" in the country, suggesting more Vatican funds may be on their way.

The Islamic State, which last month declared a "caliphate" comprising large swathes of northern Iraq and Syria, has threatened a Christian presence in the region spanning close to two millennia.

On Monday the United Nations Security Council denounced militant persecution of Christians and other minorities in Iraq, warning such actions can be considered crimes against humanity.

Before the 2003 US invasion, more than a million Christians lived in Iraq, including more than 600,000 in Baghdad and 60,000 in Mosul, as well as a substantial number in the oil city of Kirkuk and in Basra.

Until their forced exodus over the weekend, Christians had been continuously present in Mosul for about 16 centuries.