QUETTA (AFP) - A suicide bomber on Thursday killed up to 38 people and wounded more than 50 others, most of them Pakistani policemen attending a funeral ahead of the Muslim festival Eid al-Fitr.

The attack at the police headquarters in the south-western city of Quetta was the latest in a series of strikes highlighting the major security challenges faced by a newly elected government.

The bomber struck as officers gathered to pay their respects to a colleague who had been shot dead only hours before in Quetta, capital of the troubled province of Baluchistan.

Fayaz Sumbal, a deputy inspector general of police and one of the most senior officers in Quetta, was among those killed.

"At least 38 people have been killed and more than 50 injured," senior police official Mohammad Tariq told AFP. "Most of the dead and injured are policemen."

A son of the imam of the mosque at the police headquarters was among the dead, Doctor Syed Sarwar Shah told AFP at one hospital.

Mushtaq Sukhera, police chief of Baluchistan, said at least 30 people had been killed and 21 of them identified as policemen.

"The death toll may rise because the condition of most of the injured is critical," he told a news conference.

When asked whether the attacker may have been helped by an insider within the police force, he said: "Yes we will also investigate the involvement of any insider."

"Our brave officers embraced martyrdom but we will continue sacrificing our lives for the security of our motherland," he said.

There was no immediate claim of responsibility. Quetta sits on the frontline of Islamist militant violence, a Baluch separatist insurgency and violence targeting the Shiite Muslim minority.

Police said the attack was carried out by a suicide bomber. Witnesses described the horror after the explosion.

"I was inside the mosque and we were lining up for the funeral prayers when a big blast took place. I came out and saw injured and dead bodies," policeman Mohammad Hafiz told reporters."I have no words to explain what I've seen. It was horrible."

Another witness told reporters he saw bodies scattered everywhere. "Most of the bodies were beyond recognition. We collected body parts and flesh," he said in the interview broadcast by TV channel ARY.

"Those who are killing people, even inside mosques, are not human beings, they are beasts. They are not Muslims, they have nothing to do with Islam. Allah will never pardon them," he added.

The blast capped a bloody Ramadan in Pakistan, where at least 11 attacks have killed more than 120 people during the fasting month which is one of the holiest times in the Islamic calendar.

The month ends with the festival of Eid, which will begin in Pakistan on Friday.

On Wednesday, a bomb killed eight people at the end of a football tournament in Pakistan's biggest city Karachi, many of them young fans watching the game from the stands.

On Tuesday, Baluch separatist gunmen shot dead 14 people, including three security officials, 70 kilometres southeast of Quetta.