Estelle Van Der Merwe, neighbour: "I heard sounds, it seemed like somebody was involved in a fight". Photo: BBC

Mr Pistorius has pleaded not guilty to intentionally killing his girlfriend, Reeva Steenkamp.

He shot dead the 29-year-old model and reality TV star at his home, saying he mistook her for an intruder.

Estelle Van Der Merwe, a neighbour, said the row had lasted about an hour.

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At the scene

Pumza Fihlani BBC News, Pretoria

There is much heavier rain here as the second day of the trial gets under way in the capital - so there are not so many people at the entrance to the court, although the media are still here in force.

There is massive interest in the trial - it is possibly the most publicised case since Jacob Zuma was cleared of rape in 2006, three years before he became president.

And it does not take much for matters to become political here. Outside court on Monday, members of the local African National Congress Women's League sang struggle songs, telling me: "We are here for Reeva. She was killed and we want answers."

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"It seemed like somebody was involved in a fight," said Ms Van Der Merwe, who lives in the same gated Pretoria housing estate as the Paralympic athlete. "People were talking in loud voices."

The argument woke her at about 01:56 local time (23:56 GMT) and lasted about an hour. After that, she heard four loud sounds in succession.

Ms Van Der Merwe was the second witness to take the stand at the murder trial of Mr Pistorius, which began at the high court in on Monday.

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'Screams'

For the first time in South Africa, parts of the trial are being televised live, although some witness testimony, including that of Ms Van Der Merwe, is being excluded from TV broadcasts.

However, the audio of the entire trial is being aired.

Mrs Van Der Merwe told state prosecutor Gerrie Nel she had been irritated by the noise of the argument and placed a pillow on her head "in hope of falling asleep again".

Oscar Pistorius blocks his ears as he concentrates on his notes on the second day of the trial

There is intense interest in the trial in South Africa

The country was stunned when the athlete shot dead his girlfriend, Reeva Steenkamp

She could not make out what the voices were saying, she said.

The second day of the trial began with defence lawyer Barry Roux quizzing the first witness, Michelle Burger, about her account of hearing a woman's screams, a man calling for help and then four gunshots.

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The BBC's Andrew Harding in court says the defence line was clear that as Ms Steenkamp was in a closed toilet with a closed window, the screams the witness said she heard could not have come from her.

Mr Pistorius was in the bathroom where the window was open so the screams must have come from him.

Mr Roux also suggested expert evidence would prove that Ms Steenkamp would have been unable to scream between shots.

When he read out details of the bullets hitting her head, Mr Pistorius's head dropped into his hands, our correspondent says.

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Clickable 3D model of Oscar Pistorius' house

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Before she stood down from the stand, Ms Burger broke down in sobs when asked how she felt when giving her statement to police.

"It was awful to hear a shout before the shots," she said.

At the start of proceedings on Monday, Mr Roux read out a statement from the athlete, giving his version of events of how Ms Steenkamp had died, saying he believed his girlfriend was in bed when he shot at the toilet door in the early hours of Valentine's Day last year.

State prosecutors say Mr Pistorius planned the killing and shot Ms Steenkamp after a row.

If found guilty of premeditated murder, he could face life imprisonment.

He has also denied charges of illegally possessing ammunition.

There are no juries at trials in South Africa, and his fate will ultimately be decided by Judge Thokozile Masipa.

Much of the case will depend on ballistic evidence from the scene of the shooting, correspondents say.