At least 52 people were killed as security forces stormed a Catholic church in Baghdad to free dozens of hostages, Iraqi officials have said.
The gunmen had reportedly demanded the release of jailed al-Qaeda militants.
Iraqis contacted the BBC to share their thoughts on the attack. You can read their accounts below.
Lubna Naji, local resident, Baghdad
I was visiting a neighbour's house [near the church] at around 1730 local time when I heard the first explosion. Many more followed and there was intense gunfire.
The power of the multiple explosions was so high that I actually felt the house shaking.
There was also fierce shooting and the sounds of ambulances and helicopters flying in the sky.
The relative of a dear friend of mine was among the hostages. She said two priests were shot, one of them was standing right beside her. She is now in hospital but she's OK.
I'm in shock and in disbelief. This happened in a church - what next? Is this a new trend? Could a hospital or a school be next?
Al Karradah has been quiet for two to three years. We have seen terrorist attacks before back in 2003 and 2008. But the security in the area had started to improve.
People here are terrified. We need an explanation of why there was a security breach.
All Baghdadis are feeling sympathetic to the Iraqi Christians - we are all Iraqis and we are unified by this event as we all strongly condemned this horrific act.
Julie, local resident, Baghdad
The church is about 500 metres from my house. Around 1700 on Sunday I drove past the area on the way to do some shopping.
I heard shots and then explosions. I hurried back home as soon as possible.
One of my daughters has a Christian friend whom she feared would be at the church. She rang her mobile and the friend answered in hysterics - she was actually being held hostage at the time.
My daughter went to pieces at this point. There was not much we could do. We knew the army would be on the way after the explosions.
We got in touch with the young lady's family to let them know.
By midnight we heard that she had survived, but was in hospital with shrapnel injury. Her mother had also been held hostage and was also safe.
But another of my daughters has just now returned home from a funeral. Her friend's father was not so lucky - he died in the attack.
As a Muslim I am totally devastated and disgusted about what has happened. This is not what Islam is about.
The church is one of the biggest in Baghdad. Christians come from all over the city to worship there. It must be devastating for the community.
It is tremendously scary for everyone in Baghdad. We have got used to bombs and attacks - but this is something new. The attacks were different and frighteningly well organised.
Most people will blame the government for not protecting the people. We have so much security - policemen at every school gate, checkpoints everywhere. Yet the attackers still get through.
Things may have got better than the bad old days of 2006 and 2007, but we never feel safe here.
Wazir, USA - family members killed in the attack
I heard that three of my extended family were killed in the church on Sunday - my uncle's wife's sister, her husband and their 19-year-old son.
Another relative who was also in the church saw them killed and she pretended to be dead - she survived.
I lost my aunt and her husband back in 2004, right after the Christmas holidays in a similar attack.
I lived all my life in Iraq and it is really sad what is happening to us there.
The only close relatives that still live in Iraq are my two aunts - the rest of my immediate family has moved to other parts of the world.
No one would be happy to be in that environment. If I was there, I could be dead like my relatives.
I think it is important that the world understands what is happening and to tries to stop the killings.
We have changed Wazir's name to protect his identity and that of his family.