KARACHI -  Police on Sunday confirmed that an alleged incident of robbery reported in Malir area last week was actually an act of murder where a 20-year-old young woman killed her younger sister, Aleena, with the help of her fiance.

On December 6, it was reported that a 16-year-old girl was stabbed to death and her sister, Alveena, was wounded when they allegedly resisted a robbery attempt in their home.

However, addressing a press conference on Sunday, Senior Superintendent Police (SSP) Korangi Nauman Siddiqui said that Alveena had confessed to slitting the throat of her little sister after allegedly being blackmailed by Aleena and her friends for several days.

"It is an unfortunate incident," the SSP said as he opened his press conference in which he detailed the events that led to the teenage girl's murder.

According to the SSP, the deceased teenage girl and her friend, Ahsan, had been blackmailing Alveena with compromising photographs.

The SSP said that Alveena and her fiance of one and a half years, Mazhar, had at first considered killing Ahsan but decided against it.

They had then approached Kashif, another suspect who was questioned by police, for help in killing the younger sister but he had refused.

Kashif confessed to being approached by Alveena and Mazhar for the murder, the SSP said.

After he refused, the two then took it upon themselves to carry out the crime.

Siddiqui said that on December 5, Mazhar and Alveena had tried one last time to convince the 16-year-old to tell Ahsan to delete the pictures. When she refused, Mazhar held her down and Alveena slit her throat with a knife, the official said.

"She (Alveena) has confessed to it," Siddiqui said.

He said that after the murder, the accused had attempted to destroy the evidence, including mobile phones.

According to the SSP, the police had been suspicious of Alveena's involvement in the murder from the beginning but refrained from arresting her to first recover the evidence.

The police recovered six mobile phones, Rs76,000 in cash and a knife ─ the murder weapon ─ from Mazhar's house.

"Whatever the motive, they have carried out a brutal act of murder," Siddiqui said.

Responding to a question by a journalist, Siddiqui said that action should be carried out against Ahsan as well for blackmailing Alveena. The SSP was critical of the "negative use of mobile phones" and urged parents to be careful in providing the devices to their children.

The SSP credited the station house officer of Saudabad, the district superintendent police and superintendent police for solving the murder.

Addressing the press after SSP Nauman, Alveena confessed that she had killed her sister.

"She (Aleena) was torturing me mentally," the accused said. "They were threatening to upload the video on social media."

Alveena claimed that she had begged the blackmailers repeatedly to delete a compromising video of her but Aleena and her friend Ahsan had refused.

"Ahsan should not be released. He made me kill my sister," Alveena said. "I had no choice. Ahsan should be given the strictest punishment." "He made my sister make the video of me and then used it to blackmail me."