Image caption Laila says she's frustrated at the lack of any leads in the hunt for her sister

It's been three days since Dua Mangi was kidnapped from an affluent neighbourhood of Pakistan's biggest city Karachi, but there is still no trace of her.

Her friend Haris Soomro, with whom she was walking down the street when she was abducted by four or five armed men, was shot and injured by one of the assailants when he tried to resist.

He's still in hospital - reports say he was shot in the neck - and his condition is not said to be stable.

The motive behind the kidnapping is unclear, and not much detail of Dua Mangi's personal life is known, but a quick look at her Facebook page reveals her to be an educated, successful, independent woman.

However, the kidnapping might have gone unnoticed in crime-ridden Karachi as just another statistic - had it not been for a storm it raised on social media.

Image copyright Laila Mangi Image caption Dua Mangi has been missing since she was kidnapped on Saturday night

It started with her sister, Laila Mangi, posting Dua's picture on Facebook with the news she had been kidnapped. Laila asked her followers to keep an eye out and inform the family if they saw her anywhere. One of her cousins made a similar request on Twitter.

These messages attracted responses from several rights activists, but the debate soon evolved into one that was less focused on Dua's recovery and more on the way she was dressed, suggesting that - with a sleeveless top - she was asking for it.

There were also caustic comments on why she, a young woman, was roaming around with a male friend at night.

This attracted a frenzy of comments, both sympathetic and unkind, with many taking issue with the portrayal of Dua as an immodestly dressed hate figure who deserved what she got.

Many tweeters turned on Dua's critics, questioning their own moral standards.

Though the mixing of sexes is becoming increasingly common in urban areas of Pakistan, traditional conservative elements still see it as dishonourable and un-Islamic.

However, a senior police officer, Shiraz Ahmad, told the BBC that this kind of debate on social media tends to benefit the offenders, making the job of the police more difficult.

Psychologist Danika Kamal agrees.

"The debate has turned from who kidnapped the girl to why she was kidnapped. Such naming and shaming causes added pain to the affected family," she told the BBC.

She's aware of cases where "families have withdrawn similar complaints with the police just so as to avoid such public shaming".

Vendetta or ransom?

According to police, the kidnapping took place in the Khayaban-e-Bukhari area of the city, in the upmarket Defence neighbourhood. Nearby Clifton beach is dotted with restaurants and tea houses and serves as an evening rendezvous for young people from all over the city.

Dua and Harris are reported to have been at the Master Chai teashop, a favourite haunt they'd visited frequently in recent months.

Image caption A protest in support of Dua and Harris was held in Karachi on Tuesday

Police recovered both of their mobile phones from the site of the abduction. They say Dua probably dropped hers during her struggle as she was being bundled inside a car, which police say the kidnappers had stolen.

Officers have obtained CCTV footage of the area and a geo-fencing exercise of mobile phones is ongoing.

Dua is the niece of a famous Sindhi language poet and columnist, Aijaz Mangi.

He describes her as a student of law who took an "active interest in issues related to progressive politics, feminism and human rights".

"She had been studying at a college in the United States for two years, but then returned and was now studying at a law college in Karachi."

He told BBC Urdu that Dua often went with her sister Laila to the Khayaban-e-Bukhari area, where fellow students gather in the evenings over a cup of tea and unleavened fried parathas.

"On Saturday, she went there with Laila, but Laila came home early while Dua said she would return later. After about an hour and a half, one of her friends called us to say she had been kidnapped."

He said he wasn't sure if there was any personal vendetta involved, or whether ransom was the motive.

The family has since told police of their suspicions that she might have been kidnapped by a fellow student from her days in the US.

For now, where Dua is remains a mystery, but the debate about what happened to her is revealing.