Pakistanis Tuesday mourned the victims of a Taliban-claimed suicide blast in Lahore as the city's residents railed at the government for failing to protect them.

Punjab Chief Minister Shahbaz Sharif declared a day of mourning after Monday's blast, believed to be targeting police managing a busy protest in front of the Punjab Assembly at rush hour on Mall Road.

13 people were killed, emergency officials told Dawn.com, including six police officers. AFP reported the death toll to be higher at 15, with at least 87 injured.

Official funerals were held Tuesday for some of the victims.

Read more: Bomber traumatises Lahore; police bear brunt of attack

Senior police officers were trying to convince the chemists to call off the protest when the bomber, who apparently had mingled with the protesters, stepped forward to get close to the negotiators and blew himself up. The protest on The Mall was being held against recent amendments to the Drug Act which the chemists called a ‘black law’.

The toll could have been much higher, Raza said, but for two vehicles — a TV news van and a minivan belonging to the protesters — which absorbed much of the impact of the blast.

The Jamaat-ul-Ahrar faction of the banned Pakistan Tehreek-i-Taliban (TTP) claimed responsibility for the assault, which came three days after it announced it would carry out a series of attacks on government installations around the country.

Also read: Rana Sanaullah shifts blame on protesters

Lahore residents vented their fury at the militants and the government at the blast site early Tuesday.

“They (the militants) have no link with Islam nor do they believe in any religion, the only thing they know is killing people, this is utterly an act of terrorism,” Tariq Saleem told AFP.

Nadeem Akhter called on the government to do more to bring the situation under control. “Our children and people are being killed in these attacks,” he said.

Both British High Commissioner to Pakistan Thomas Drew and US ambassador David Hale branded the attack “cowardly” in separate statements, expressing support for the victims, while the EU said it was “shocked and saddened” by the incident.

The attack underscored the challenges faced by the country in its push to stamp out militancy, even though security dramatically improved in 2015 and 2016.

Homegrown groups like the umbrella TTP retain the ability to carry out spectacular attacks, despite a military-led crackdown on extremism.

Lahore suffered one of Pakistan's deadliest attacks in 2016 — a Jamaat-ul-Ahrar suicide bombing in a park last Easter that killed more than 70 including many children.

But such incidents have been rare in the city in recent years.