On Monday afternoon, 20-year-old goldsmith Hassan Ahmed was heading back home from work on his motorbike and passing by Lahore's busy Mall Road.

Hundreds of pharmacists were rallying against changes to a drug sale law, outside of the provincial assembly building.

There was a sudden blast.

"That is exactly when the suicide bomber detonated the bomb and we lost Hassan," Saqib Rehman, Hassan's longtime friend, told Al Jazeera.

"[Hassan] was the sole breadwinner of his family of 10. He passed away at a very young age. Why was there not enough security to stop cars and bikes from passing by?"

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At least 13 people were killed in the attack, including seven police officers and six civilians.

Within hours, the Pakistani Taliban faction Jamaat-ul-Ahrar claimed responsibility for the blast.

A spokesman for the group warned in a statement that Monday's bomb was "just the start".

Pakistanis across the Pubjab province mourned the victims on Tuesday, blaming poor security measures.

Most of the markets and businesses were closed and lawyers boycotted court proceedings in the provincial capital.

Punjab's government declared one day of mourning with the national flag lowered to half-staff at all government buildings.

Lahore residents are "furious" at the armed groups conducting attacks, Rehman said, adding that "people here feel the attacks will increase in the near future".

"If this suicide bomber could conduct an attack this easily, it tells us that we are not safe or protected."

Poor security

Monday's attack underlines Pakistan's challenges of eliminating armed groups and improving security.

"The attacker was not targeting civilians, he went directly towards the police officials who were negotiating with the protesters," said Arshad Dogar, a crime reporter for The News, a local newspaper.

Dogar had been covering the rally and was present at the time of the attack.

"In a situation like this, where there are about 2,000 people gathered together, the security measures were close to zero," Dogar told Al Jazeera.

"No one was being checked. Anyone could come and participate in the rally. The suicide attacker walked in without any hurdles and successfully conducted the attack."

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In 2016, Lahore suffered one of Pakistan's deadliest assaults when a suicide attack in a park killed more than 70 people, including many children.

Jamaat-ul-Ahrar group, which claimed that attack, said it was targeting members of Pakistan's Christian minority who had gathered there to celebrate Easter Sunday.

Jamaat-ul-Ahrar also claimed responsibility for a bombing at a hospital in Quetta that killed 74 people in August last year.

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