At least 20 people were killed and over 50 others injured when Pakistani Taliban militants attacked a Shia mosque in Peshawar city during Friday prayers, sparking protests across cities, police and hospital officials said.

The Tehreek-e-Taliban Pakistan (TTP) claimed responsibility for the attack, Dawn reported citing an email sent by the group.

Heavy firing was also reported and residents said a thick cloud of smoke engulfed the Hayatabad area of the city.

Residents said three explosions took place inside the Imamia Masjid at the time of Friday prayers.

The attack comes two weeks after a suicide bombing at a Shia mosque in Shikarpur in Sindh province which killed over 6o people, the deadliest sectarian incident to hit the country in nearly two years.

Agitations and protests were reported from different cities, including Peshawar, Karachi and Islamabad. People burnt tyres, blocked roads and chanted slogans denouncing militants and attacks on worshippers, Dawn online reported.

The Muttahida Majlis Wahdatul Muslimeen (MWM), Shia Ulema Council, Jaffria Alliance and Imamia Rabita Council have announced a three-day mourning.

Mushtaq Ghani, information minister of Khyber Pakhtunkhwa province, called for deployment of Frontier Corps personnel, saying the mosque was very close to tribal areas, which made access for terrorists easy.

A police and army personnel-led operation at the mosque after the militant attack ended with the officials saying that one of the suicide bombers’ jacket had been defused.

Shia scholar Arif Hussain said there was no one to control terrorists, adding that these attacks would continue if they are not brought under control.

“They are enemies of the state and enemies of Islam,” he said.

Khyber Pakhtunkhwa (KP) Inspector General of Police Nasir Durrani said the attackers did not enter the mosque through the main gate as security personnel were deployed there.

In an earlier report, Ghani confirmed that 19 people were killed in the attack.

Hayatabad came under heavy surveillance as helicopters hovered over the area and dozens of FC troops took up position to clear the vicinity.

Prime Minister Nawaz Sharif and President Mamnoon Hussain issued strong condemnation of the incident.

Political leaders, including Pakistan Tehreek-i-Insaf chairman Imran Khan, Jamaat-i-Islami (JI) leader Sirajul Haq, and Muttahida Qaumi Movement (MQM) chief Altaf Hussain also condemned the attack.