ISLAMABAD: Police said on Friday they have arrested six men suspected of being behind a string of high-profile killings and assassination attempts linked to a banned sectarian group.

The arrests are a rare success for the police, who have a notoriously low detection and prosecution rate for such crimes.

Police said the six suspects are responsible for killing 16 people over the last two years and for four attempted murders.

Their victims are believed to include a lawyer, a well-known Pakistani journalist, and a prominent Shia doctor and his 12-year-old son gunned down on their way to school.

They are also thought to be behind an attack last month in which writer Raza Rumi, a vocal critic of the Taliban, was wounded and his driver killed.

The men are connected to banned sectarian group Lashkar-i-Jhangvi, the police statement said, and have admitted receiving instructions from its leader Malik Ishaq.

“These cruel criminals are involved in these heinous crimes by pretending to be a religious group, including crimes like murder, attempted murder, kidnap for ransom, illegal armament and drugs,” the statement said.

The statement identified Abdul Rauf Gujjar as the main hitman in the killings.

“He came to this direction through Malik Ishaq,” the statement said.

“He further revealed that he was a member of illegal and outlawed organization Lashkar-i-Jhangvi.”

Ishaq spent 14 years in jail on terrorism and attempted murder charges that were eventually dropped in 2011, partly due to witness intimidation, police said.

Lashkar-i-Jhangvi has claimed responsibility for killing hundreds of Shia's, who make up about 20 per cent of Pakistan's population.

The militant group wants to chase Shia's out of Pakistan and establish a hardline Sunni theocratic state in the nuclear-armed nation of 180 million people.

The Pakistani government has often been accused of being soft on militants, and the largely poorly trained and under-resourced police usually struggle to investigate and arrest suspects.

Friday's statement said that a special unit had discovered forensic evidence implicating the men, and that drugs and weapons had also been recovered.

Arrests do not always lead to convictions, however, and Pakistan's courts have a very low conviction rate even for high-profile cases of militancy. Judges and prosecutors complain they are frequently intimidated by militants.