A suicide bomber injured four policemen, one critically, outside a Shia mosque in southern Pakistan as the country marked the beginning of the religious festival Eid al-Adha on Tuesday.

The attack took place in Shikarpur in Sindh province, around 470 kilometres (300 miles) north of Karachi and the same district where at least 61 were killed in a suicide attack on another Shia mosque in 2015.

Officials said two suicide bombers tried to enter the Khanpur Imambargah but were intercepted by police.

‘Four of our men are injured of whom one is critical,’ Umar Tufail, a senior local police officer told AFP.

Tufail added doctors were also trying to save the life of the other suspected bomber, who was injured when the first one blew himself up but failed to detonate himself.

‘The attackers came as the worshippers were gathering to offer Eid prayers. Police were able to stop him at the gate outside the mosque,’ A.D. Khawaja, chief of police for Sindh province said.

Worshippers overpowered the second would-be suicide bomber as the police were reeling from their injuries, he added.

Pakistan has been hit by frequent sectarian violence in recent years, most of it perpetrated by hardline Sunni Muslim groups against minority Shia Muslims, who make up around one in five of the population.

The January 2015 attack on the Shias in Shikarpur, blamed on the Sunni militant Lashkar-e-Jhangvi group, led to a wave of nationwide protests.

In another incident Tuesday, a police van was hit by a roadside bomb in Quetta city in the southwestern province of Baluchistan.

‘One policeman was killed and five others injured when their van was targeted,’ local police official Abdul Razaq told AFP.

He said two of the injured were in critical condition.

The incident was confirmed by local administration official Akbar Harifal.

Baluchistan, which borders Iran and Afghanistan, has oil and gas resources but is afflicted by Islamist militancy, sectarian violence between Sunni and Shia Muslims and a separatist insurgency.