Image copyright AFP/Getty Images Image caption The letter said so-called Islamic State was targeting minority groups such as the Yazidis

The killing of minorities by so-called Islamic State should be recognised as genocide, more than 60 parliamentarians have said in a letter to the PM.

They urge David Cameron to use his influence to reach an agreement with the UN that the term genocide be used.

This would send the message that those responsible would be caught, tried and punished, the letter adds.

IS has been systematically killing minority groups including Iraqi and Syrian Christians and Yazidis, it said.

The UN has cited the Yazidis' treatment by IS as evidence that IS may have committed genocide and war crimes in Iraq.

The jihadist group has also been trying to eradicate minority groups from large parts of the country, human rights organisations have warned.

'Not semantics'

The letter, written by MP Rob Flello and Lord Alton, said there was clear evidence of IS assassinations of church leaders, mass murders, torture, kidnapping for ransom in the Christian communities of Iraq and Syria and "the sexual enslavement and systematic rape of Christian girls and women".

Image copyright AP

It also said the group was carrying out "forcible conversions to Islam", the destruction of churches, monasteries, cemeteries, and Christian artifacts, and theft of lands and wealth from Christian clergy.

The letter said: "This is not simply a matter of semantics.

"There would be two main benefits from the acceptance by the UN that genocide is being perpetrated.

"First, it would send a very clear message to those organising and undertaking this slaughter that at some point in the future they will be held accountable by the international community for their actions; they will be caught, tried and punished.

"Second, it would encourage the 127 nations that are signatories to the Convention to face up to their duty to take the necessary action to 'prevent and punish' the perpetrators of these evil acts."

UN definition of genocide:

Article II of the 1948 U.N. Genocide Convention says: "Genocide means any of the following acts committed with intent to destroy, in whole or in part, a national, ethnical, racial or religious group, as such:

Killing members of the group; Deliberately inflicting on the group conditions of life calculated to bring about its physical destruction in whole or in part;

Imposing measures intended to prevent births within the group;

Forcibly transferring children of the group to another group."

Earlier this year, a report by the human rights organisation Minority Rights Group detailed summary executions, forced conversions, rape and other abuses suffered by minorities in Iraq.

IS first emerged in Syria, fighting President Bashar al-Assad during the ongoing civil war there.

In June 2014, the group formally declared the establishment of a "caliphate" - a state governed in accordance with Islamic law, or Sharia, by God's deputy on Earth, or caliph.

IS members are jihadists who adhere to an extreme interpretation of Sunni Islam and consider themselves the only true believers. They hold that the rest of the world is made up of unbelievers who seek to destroy Islam, justifying attacks against other Muslims and non-Muslims alike.

Beheadings, crucifixions and mass shootings have been used to terrorise their enemies. IS members have justified such atrocities by citing the Koran and Hadith, but Muslims have denounced them.