Witnesses told of the horror at the Al Noor Mosque in Christchurch as a gunman burst in shooting at worshippers, mowing them down with automatic weapons fire.
It was one of two mosques targeted in the New Zealand city.
"I could hear screaming and crying. I saw some people drop dead, some people were running away," a man in a wheelchair, who was at the mosque during the incident, told news outlet TVNZ. He said he had yet to see his wife, who was also inside the mosque yesterday.
The man said the start of Friday prayers had been peaceful: "You could hear a pin drop.
"Then suddenly, the shooting started. It started in the main room.
"I was in the side room, so I didn't see who was shooting, but I saw that some people were running out to my room where I was. I saw some people had blood on their body and some people were limping. It was at that moment I realised things were really serious."
He added: "I tried to get out, and I pushed myself out the back where my car was, and from there, I heard the shooting. It went on for six minutes or more."
Another witness, Mr Len Peneha, who lives next to the mosque, said he saw a man dressed in black enter the mosque at about 1.45pm local time (8.45am Singapore time), and then heard dozens of shots, followed by people running from the mosque in terror.
He said the gunman ran out of the mosque, dropped what appeared to be a semi-automatic weapon in his driveway, and fled.
"I saw dead people everywhere. There were three in the hallway, at the door leading into the mosque, and people inside the mosque.
"It is unbelievably nutty. I don't understand how anyone could do this to these people, to anyone. It is ridiculous."
One teen witness said he ran as fast as he could and hopped over the fence to Hagley Park, which is opposite the mosque.
"I didn't stop. The gunshots sounded like pop, pop, pop... I heard over 50," he said.
A man who wanted to be known only as Mr Nour told the Christchurch Star newspaper that he crawled to safety during the shooting. He said he was in the front row when the gunman came in.
"First, he shot people outside. Then he came in the front," he said. He heard the gun being reloaded about three times.
The gunman began shooting in all directions. "I saw people drop dead in front of me. I was crawling to get away," he said.
Mr Nour added that he crawled across the floor of the mosque to a window that had been broken by others as they fled and jumped through it. He jumped over a neighbouring wall and ran around the block, and could still hear shooting.
Mr Mohan Ibrahim described to the New Zealand Herald how he ran for his life to escape the gunman. He was one of 200 people in the Al Noor Mosque when he heard shots being fired. "At first, we thought it was an electric shock, but then all these people started running."
He said there had been lots of people killed and many injured.
"I have been calling my friends, but there are many I have not heard from. I am scared for my friends' lives," he said.
A separate shooting also occurred at the Linwood Mosque in Christchurch. It was not immediately clear if the attacks at the two mosques were carried out by the same man.
The stuff.co.nz news portal quoted witness Syed Ahmed as saying that a man wearing a black motorcycle helmet and camouflage clothing, carrying what he thought was a black assault rifle with white writing, started shooting indiscriminately from outside the mosque.
The man first shot several elderly people sitting on chairs during prayers, Mr Syed said. "They were basically all shot."
He said he thought that at least eight people had been shot, including at least three women and two of his friends.
One of those killed had been shot in the head and remained inside the mosque, Mr Syed added.
The gunman came through the front door shouting something, but it "could not be heard over the screaming", he said.
Mr Syed said he kept low on the ground and crawled to the storeroom before getting away.