Image caption Sipah-e-Sahaba is thought to have carried out scores of mainly sectarian attacks over the years, but the video is the focus of its latest rallying cry

Protests in Pakistan against an anti-Islam film made in the US began peacefully. But last week, after Friday prayers, at least 21 people were killed in demonstrations across the country. Aleem Maqbool reports from Karachi, the city which saw the worst of the violence, and where more protests are planned.

Women from the Karachi neighbourhood of Usmanabad have been gathering every day since policeman Muhammed Tufail died.

They have been trying to comfort his mother, Mariam, and praying.

"Weren't the policemen Muslims too?" asks Mariam. "My son had been upset by the video too.

"They were just doing their job, and the protesters treated them like enemies."

'So proud'

The family had been watching the news channels when it all happened.

Even if the whole world is destroyed, we will not stop our demonstrations for this noble cause Aurangzeb Farooqi, Cleric and Karachi head of Sipah-e-Sihaba

They knew the protests had been planned and saw coverage of the crowds growing in the centre of Karachi.

They watched with horror as the demonstrators became more violent and confronted the police.

Ultimately on live television they saw footage of their son lying on the ground then being carried, limp, from the scene.

They rushed to the hospital to find his body already in the morgue.

"We were so proud of him," says Mariam. "He was bright and cared about educating his four children and teaching them about Islam.

"Now they will grow up without a father. Why?" she cries.

As we leave, Tufail's youngest brother, Amir approaches us.

"He died defending the American consulate," he says.

"He took a bullet for them, not in his back, but in his chest. I hope the Americans appreciate what he did. It would be nice if they at least said 'thank you' to my parents."

Biggest demonstrations

The traffic is flowing again over the spot where police tried to hold back the protesters and where Muhammed Tufail fell.

Image caption Police came under sustained attack during the 21 September protests in Karachi

There are few signs of the battle that raged just across the carriageway and close to the American consulate.

But the turmoil led to 15 lives being lost that day in Karachi, most of them protesters.

Eight belonged to the Sipah-e-Sahaba extremist group that had organised one of the biggest demonstrations.

"It was for the honour of the Prophet," says cleric Aurangzeb Farooqi, the head of the Karachi branch of this supposedly banned organisation.

He talks of the anger felt around the Muslim world because of the anti-Islam video.

Sipah-e-Sahaba is thought to have carried out scores of mainly sectarian attacks over the years, but it is the video that has become the focus of its latest rallying cry.

'Martyrs'

"We wanted a peaceful demonstration, but they forced us to fight," Mr Farooqi said.

I hope the Americans appreciate what he did. It would be nice if they at least said 'thank you' to my parents Amir, Muhammed Tufail's youngest brother

"The violence was a conspiracy aimed at making us stop our protests, but we won't."

He demands the expulsion of the American ambassador, and tells us the protests will continue until the video maker is arrested and prosecuted.

He says more protest gatherings are planned for the coming days.

"Even if the whole world is destroyed, we will not stop our demonstrations for this noble cause."

The cleric said that those who died last week, including the police, were "martyrs".

But it is hard for Noor Jehan to accept. We find her rocking back and forth on her bed, telling herself that her son Bashir, 17, is in heaven.

Bashir was a Sipah-e-Sihaba recruit, and was shot dead at the protest.

"Everyone is telling me to be strong, and I know he died for a good cause, but I can't stop my tears," she says.

Cleric Aurangzeb Farooqi says she should be proud of her son and of the "success he had in his mission".

He is urging other young men to join the demonstrations, saying it is the only way to send the right message to the world.

But Noor Jehan suddenly seems oblivious to his words and our presence as she starts to hold a conversation with the image of her son in a photograph.