ISLAMABAD: January 13, 2016. (Reuters) Pakistan has arrested the head of the Jaish-e-Mohammad militant group on suspicion his outfit masterminded an attack this month on an air base in India, two officials said on Wednesday. Maulana Masood Azhar, an Islamist hardliner who was blamed for a 2001 attack on India's parliament, was detained two days ago along with his brother and brother-in-law and will remain in protective custody for at least 30 days, a senior intelligence official told Reuters. Pakistan said earlier in the day that it had arrested several members of Azhar's group and sealed off its offices as it investigates Indian assertions that the Jan. 2 attack, in which seven military personnel were killed, was the work of the Pakistan-based militants. The foreign secretaries of India and Pakistan - longtime, nuclear-armed arch-rivals on the Indian subcontinent - are set to hold a rare, previously scheduled meeting on Friday, part of a budding diplomatic thaw after decades of hostility. But India has demanded Pakistan take "prompt and decisive" action over the Jan. 2 air base attack before the meeting goes ahead. "We will keep them (Azhar and brothers) for as long as we need to carry out our investigation over India's claims about the attack. We are resolved to take this investigation to its conclusion," the senior intelligence official said. A senior government official close to the investigation said that Azhar, who has been placed under house arrest in the past but never prosecuted, would be prosecuted this time if evidence connected him to the attack on the Pathankot air base. On Wednesday, Pakistan took the unusual step of announcing a high-level team to investigate the incident, naming some of the country's top counter-terrorism officers and officials from both military and civilian intelligence. India's foreign ministry had no immediate comment, but said earlier it would decide late on Wednesday whether Foreign Secretary Subrahmanyam Jaishankar would travel to Islamabad on Friday for the meeting. Islamabad, which India has long accused of backing Islamist militant attacks, promised to get to the bottom of who was behind the assault on the air base after India handed evidence to Pakistan that it said implicated Jaish-e-Mohammad. The Pakistani prime minister's office said the government had made "considerable progress" in investigating the attack, and it wanted to send a team of special investigators to the Pathankot air base. "Based on the initial investigations in Pakistan, and the information provided, several individuals belonging to Jaish-e-Mohammad, have been apprehended," the office of Prime Minister Nawaz Sharif said. "The offices of the organization are also being traced and sealed. Further investigations are under way." Jaish-e-Mohammad (Army of Mohammad) has long fought Indian forces in India's part of the disputed region of Kashmir. It is blamed for the 2001 assault on India's parliament that brought the two countries to the brink of war. India also holds Pakistan-based militants responsible for the 2008 Mumbai shooting attacks that left 166 dead. But a surprise Dec. 25 visit by Indian Prime Minister Narendra Modi to meet Sharif raised hope that stop-and-start talks between the bitter rivals might finally yield progress.