Alleged mastermind among four arrested after Pakistan mosque blast

Thousands gathered in Islamabad to mourn the 32 victims of Friday's attack

Four people have been arrested on suspicion of facilitating a suicide bombing that killed more than 30 people on Friday, Pakistan's interior minister has said.

Mohsin Naqvi said an Afghan national who is alleged to be the mastermind behind the attack was among those detained. One counter-terrorism officer was killed and three more were wounded in the raids to arrest the suspects, he added.

The Islamic State group has claimed responsibility for the bombing that targeted Friday prayers at the Shia mosque in the Tarlai area, when it was packed with worshippers.

More than 160 people were injured in the blast, which was the deadliest in the capital for more than a decade.

Huge crowds were seen in the city on Saturday, as thousands of mourners gathered for the funerals of the bombing's 32 victims.

Funeral prayers took place amid tightened security, with soldiers standing guard and police checkpoints set up in key areas.

Ashiq Hussain, who lost his 21-year-old nephew Mujtaba Ali in the attack, told the Reuters news agency his family was "broken".

Condemning the attack on Friday, Pakistan's Prime Minister Shehbaz Sharif expressed "deep grief". The country's President, Asif Ali Zardari, said "targeting innocent civilians is a crime against humanity".

Eyewitnesses and survivors of the blast have told the BBC how the attack unfolded, with one saying he "lost his senses" in the moments after the explosion and another saying he saw bodies "lying everywhere".

Announcing the arrests on Saturday, Naqvi accused India of funding those behind the attack and giving them targets. The Indian foreign ministry has condemned the bombing, and rejected accusations of its involvement as "baseless".

Pakistani Defence Minister Khawaja Asif on Friday suggested Afghanistan had been involved in the attack. The Afghan Taliban government described Asif's comments as "regrettable", saying he alleged its involvement "without presenting any credible evidence".

Naqvi has pledged to increase security in Islamabad, including by recruiting thousands of new police officers and improving the city's smart security systems.

Attacks are relatively rare in the capital, although one in November left 12 dead and another 27 injured.

The blast on Friday comes after a week of violence which saw 58 civilians killed in coordinated attacks in the province of Balochistan.

The Balochistan Liberation Army (BLA) rebel group said it was behind the attacks. The military - which has been fighting an insurgency in the region for decades - said it had killed more than 200 militants in response.