Prominent buildings are being lit up red today in an act of solidarity with victims of persecution as part of RedWednesday.
In London, buildings turning red include the Foreign and Commonwealth Office, Westminster Cathedral and the official residence of the Archbishop of Canterbury, Lambeth Palace.
Elsewhere, the Mersey Gateway near Liverpool and the Sir Chris Hoy Velodrome in Glasgow will also be lit up red.
RedWednesday is a campaign led by Catholic charity Aid to the Church in Need to highlight the plight of people suffering hardship, violence or discrimination because of their faith.
A candlelit Cross procession will leave from Parliament Square today at 6:15pm led by Rehman Chishti MP, the Prime Minister's Special Envoy for Freedom of Religion or Belief.
The procession will culminate at Westminster Cathedral with a liturgy focusing on persecuted Christians in countries such as Iraq, Pakistan, and Nigeria.
This year's RedWednesday takes place after a major report by the Bishop of Truro for the Foreign and Commonwealth Office warned that the persecution of Christians was reaching genocidal levels.
ACN's own report, Persecuted and Forgotten?, recently warned that Christianity in parts of Iraq and Syria is approaching the point of total extinction following genocide carried out by Daesh (ISIS).
The report revealed a dramatic fall in the Christian population in Iraq by over 90%, from 1.5 million before 2003 to less than 150,000 today.
In response to the report, former Foreign Secretary Jeremy Hunt tabled an early day motion, calling on the government to help Christians in Iraq and Syria, that was signed by 43 parliamentarians.
Patricia Hatton, Head of Fundraising and Marketing at ACN (UK), who launched #RedWednesday, said: "Following the endorsement of #RedWednesday in the Bishop of Truro's review into FCO support for persecuted Christians – commissioned by former Foreign Secretary Jeremy Hunt – the procession is a real chance for Christians to stand together and in a very visible way, show that the lives of Christians and other persecuted minorities matter.
"We urge individuals and groups to come along – to add your voice to the call to stop the persecution of Christians and other faith groups."