QUETTA, Pakistan — Police in southwestern Pakistan have detained 36 people, mostly Afghan refugees, for questioning about a suicide bombing inside a courtroom that killed a judge and 15 other people, an official said yesterday.The suicide bomber struck a crowded courtroom in the city of Quetta on Saturday in the deadliest of a series of attacks in recent weeks.

There is suspicion in Pakistan that local pro-Taliban militants are targeting sensitive sites to undermine the country’s support of the United States. An official in the region where Saturday’s attack took place hinted at Afghan involvement, but he offered no proof.

The explosion also wounded 24 people and left bloodied clothes and body parts scattered next to wrecked furniture and shattered glass in the Quetta District Courts. It forced police — already on alert — to further tighten security nationwide.

The chief of police in Quetta, the capital of Baluchistan province, said Sunday that 36 people, including at least 22 Afghan refugees living in the city, have been detained in a probe into the bombing.

“We will investigate them to determine whether anyone among them has any link with the incident,” said police chief Raho Khan Brohi.

The men were picked up in separate raids across Quetta late Saturday but no one was a suspect or formally arrested in the case, Brohi said.

“Afghans have been involved in previous such attacks here. I cannot rule out their involvement,” said Jam Mohammed Yousaf, the top elected official in Baluchistan, on Saturday. “We don’t have any evidence to prove it,” he added.

Relations between the neighboring countries have soured over Afghan allegations that Pakistan is supporting Taliban militants who have escalated their campaign of violence in the neighbouring country over the past year. Pakistan denies helping the militants but acknowledges that some operate from its soil.

Increasingly, it appears Pakistan itself has become a battleground. There have been about 10 bombings in the past month, mostly in the northwest, but the capital Islamabad has also been targeted in suicide attacks at its international airport and the Marriott Hotel.

Saturday’s blast in Quetta, a city where Taliban activists and leaders are alleged to hide, was by far the deadliest.

The suicide bomber “entered the courtroom on foot and he immediately exploded himself,” Yousaf said.

The blast killed Judge Abdul Wahid, five lawyers and some of the relatives of prisoners who were on trial, Yousaf said. He could not give details about the prisoners’ identities or the cases being heard. The attacker died, along with 15 others.

Some 2,500 people attended the judge’s funeral yesterday, Quetta Mayor Mir Maqbool Ahmed Lehri told The Associated Press.

Police have recovered the head and other body parts of the suspected bomber, and the remains have been sent to a hospital near the capital Islamabad for DNA tests, an intelligence official said yesterday.

The suspect, a man who appears to be in his late 30s, had curly hair and a short beard, the official said, without speculating on the man’s nationality.

The Quetta attack came a day after police near Islamabad and southern city of Karachi said that they had arrested five militants who were allegedly planning suicide attacks on foreigners and minority Shiite Muslims. Also, police in the southern city of Sukkr said Saturday they had arrested three militants planning suicide attacks at upcoming Shiite gatherings.