Image copyright Powerplay/ARY News Image caption A screen grab from TV said to show Hassan Niazi

Police in Pakistan say they are seeking to arrest PM Imran Khan's nephew for taking part in a violent protest at a hospital in which three patients died.

Lahore police raided Hassan Niazi's residence and say he may now be hiding.

Mr Niazi was among several hundred lawyers who ransacked a city hospital in a dispute with doctors. Riot police had to be called in to restore order.

Images of lawyers - in suits and ties - assaulting staff and damaging property prompted shock and condemnation.

Photos and videos of Hassan Niazi were widely shared on social media, as people lined up to criticise the lawyers.

Mr Niazi has admitted taking part in the violence at Lahore's Punjab Institute of Cardiology (PIC) and said on Twitter he regretted it.

From his uncle, who tweets often, there has been no mention of the furore over his family's link to Wednesday's violence.

Mr Khan's nephew is prominent in footage of the attack, and can be seen participating in physical assaults as well as an arson attack in which a police van was set on fire.

The lawyer and human rights activist was held soon afterwards by police and was seen being escorted out of the area.

So there was surprise when his name did not appear in the police report listing those lawyers facing court action in connection with the violence.

Media playback is unsupported on your device Media caption The incident was sparked by a dispute between the lawyers and the hospital

The authorities have not explained what happened after he was detained, but a spokesman for the city's police chief said Mr Niazi had been identified through video footage and was now being sought.

"His residence in Lahore was raided by the police last night and also this morning to arrest him, but he was not found there and has possibly gone into hiding," the spokesman, Waseem Butt, told BBC Urdu's Shahzad Malik.

Many are questioning this account. Some wonder whether he was freed because he is related to the prime minister. Opposition politicians are demanding Mr Niazi's immediate arrest.

Image copyright EPA Image caption Some patients had to be moved outside the hospital after it was stormed by lawyers

More than 80 lawyers were arrested over the hospital attack, and 46 have been remanded in custody. Lawyers called a nationwide strike on Friday, angry at police treatment of their colleagues in Lahore.

But headlines, editorials and social media outrage suggested they were out of step with others in the country.

One article in Dawn newspaper described the attack as "a stain on our collective humanity". Other commentators said it was a new low for Pakistani society's sinking levels of tolerance which is giving way to mob justice.

What led to the violence?

The lawyers had been protesting over the alleged mistreatment of some of their colleagues by hospital staff last month.

Image copyright AFP Image caption Police clashed with lawyers who marched on the hospital to confront doctors

But the final trigger for the violence appears to have been a video posted on social media by a doctor on Tuesday night in which he poked fun at the lawyers.

Video showed the lawyers ransacking wards at the hospital the next day, beating staff and smashing equipment. As panic spread, doctors and paramedics hid, leaving patients unattended, including those in a critical state.

Hospital sources said at least three patients - a woman and two men - died because doctors could not attend to them during the violence. It is believed that the woman had been in the intensive care unit.

Riot police fired tear gas and took more than two hours to restore order, officials said.