ISLAMABAD, PAKISTAN - Pakistani Prime Minister Imran Khan has directly accused rival India of being behind a deadly terrorist attack on his country's stock exchange building in Karachi.

Four heavily armed assailants attempted to storm the key economic installation in the southern port city Monday, but security guards swiftly confronted and killed them in a shootout that officials said lasted eight minutes.

The firefight also killed four other people, including private security guards and a police officer.

"India had wanted to destabilize Pakistan through this attack. ... We have absolutely no doubt that it was planned in India," Khan told Parliament on Tuesday.

Khan's allegations came a day after India denied any links to the assault.

An outlawed militant group, the Baloch Liberation Army (BLA), a U.S.-designated global terrorist group, claimed responsibility.

The group is largely active in and fighting for independence of Pakistan's southwestern natural resource-rich Balochistan province, along with several other separatist organizations.

Islamabad consistently blames New Delhi for supporting the militants.

The BLA also took responsibility for an attack on the Chinese consulate in Karachi in 2018. The group has repeatedly threatened to attack China's Belt and Road Initiative-related investments in Balochistan.

The terror outfit said Monday that the stock exchange building in Karachi was attacked because Chinese companies also partially own it.

Khan said Tuesday the attack could have ended up as a "major tragedy" had Pakistani security forces not responded rapidly to neutralize it. He noted the militants had come well-prepared with a heavy supply of arms and equipment to take people hostage and massacre them inside the stock exchange building.

"For the last two months, my Cabinet has known, and I had informed my ministers (about such an attack). But all our (security) agencies were on high alert," Khan said, without providing any evidence.

Monday's assault came amid tension between Pakistan and India over a territorial dispute regarding Kashmir.

Military skirmishes between the nuclear-armed countries across the cease-fire line in the divided Himalayan region have become an almost daily occurrence in recent months, inflicting casualties on both sides.

Earlier in June, New Delhi ordered Pakistan to reduce the size of its embassy staff by half, accusing Pakistani officials of espionage.

Islamabad rejected the charges as baseless and retaliated by ordering India to pull out half of its staff from the Indian High Commission in Pakistan.