The statement came from Tehrik-i-Taliban Pakistan (TTP), otherwise known as the Pakistani Taliban, congratulating the Afghan Taliban on their “blessed victory”.

For many, Tuesday’s message was an ominous sign of what the Taliban takeover of Afghanistan could mean for Pakistan. While politicians, clerics, military officers and even the prime minister, Imran Khan, were among those in Pakistan celebrating the establishment of Taliban rule – Khan describing it as Afghanistan breaking “the shackles of slavery” – there are deep concerns that it will embolden powerful Islamic militant organisations operating in Pakistan.

These militant groups are fighting for Pakistan to adopt a similar model of strict and repressive Islamic governance seen under Taliban rule in Afghanistan between 1996 and 2001, and which many believe will once again be imposed.

“The Taliban takeover will empower all extremist-religious elements in Pakistan” said Ayesha Siddiqa, an author and political analyst. “The next few months will probably be peaceful in comparison to what lies ahead in Afghanistan but then extremism will start. If the Taliban succeed in any form, it will give militants reason to argue for an Islamic system to govern Pakistan.”

TTP, which is a banned militant group in Pakistan responsible for dozens of terrorist attacks, had already been making a resurgence recently. The group is an offshoot of the Afghan Taliban and their ties and shared ideology are undeniable; in the past, senior Taliban figures have been made TTP leaders.

Among the first prisoners released by the Taliban in Afghanistan last week was the TTP deputy chief, Faqir Muhammad. Even senior military leaders in Pakistan are reported to have admitted recently to lawmakers that the Afghan Taliban and TTP are “two faces of the same coin”.

Many blame Pakistan for the resurgence of the Taliban in Afghanistan, with whom it has historically always been friendly. Pakistan helped bring about and supported the first Taliban regime in 1996, and after the US invasion in 2001 Taliban leaders were given sanctuary in Pakistan, where they lived and regrouped for two decades.

Pakistan has been accused of turning a blind eye to the Taliban training camps in the remote and rugged border regions. Madrassas – Islamic religious schools – across Pakistan have been found to be key recruiters of jihadist militants, sending young men to fight for the Taliban in Afghanistan.

As the battles between insurgents and Afghan government forces escalated in recent weeks, injured Taliban fighters were allowed to cross over the border for treatment, the bodies of dead Taliban soldiers were brought back to Pakistan and pro-Taliban marches and rallies in Pakistan’s border regions continued.

It is not known exactly what Pakistan hopes to gain from Taliban rule in Afghanistan this time round, though it is likely they are pushing for greater influence and leverage in Afghanistan and a regional ally against India, their greatest foe. Khan’s dislike for the US-backed Afghan government, led by Ashraf Ghani, was also well known.

Ghani was seen to be too friendly with India and he had publicly accused Pakistan of allowing 10,000 jihadist fighters to cross into Afghanistan, which Khan denied. Pakistan has also paid a very heavy price for the two decades of US military presence in the region, with 80,000 lives lost in the so-called war on terror.

Among those in Pakistan who expressed support for the Taliban takeover in Afghanistan was Asad Durrani, a former chief of the powerful Inter-Services Intelligence (ISI) spy agency. “The masses will be happy the Taliban took over Afghanistan,” Durrani told the Guardian. “Concerns are mostly among the privileged classes who will be deprived of their loot, and their clout to exploit the poor.”

Durrani, who was instrumental in the creation and rise of Taliban in the 1990s when he led ISI, praised their Islamic model of governance. “The problem is that the Taliban do not intend to influence politics or ideology in Pakistan,” he added. “But it’s entirely up to us if we want to adopt their victorious model.”

Yet many fear that Pakistan is playing a risky game by supporting the Taliban in Afghanistan while simultaneously fighting against TTP in Pakistan. “Pakistan has allowed the Taliban to live in Pakistan and I think the consequences of this are going to be serious,” said Ahmed Rashid, the author of Taliban: Militant Islam, Oil and Fundamentalism in Central Asia. “There is going to be a huge upsurge of fundamentalism and extremism in Pakistan.”

On Monday, while responding to questions about the release of the TTP leaders from the prisons in Afghanistan, the Taliban spokesperson Sohail Shaheen said: “We won’t allow anyone to use Afghanistan’s soil for terrorism.”

However, Rashid said the Pakistani security establishment was misguided to believe that the Afghan Taliban would not continue to shelter and support the TTP and other militant groups that threaten Pakistan, including al-Qaida, as they had already been doing. TTP fighters are already said to have crossed over to Afghanistan to help the Taliban take back Afghanistan.

“There is no way the Taliban will give up TTP fighters and send them back to the prisons of Pakistan,” he added. “Pakistan was an ally to the Afghan Taliban, giving them shelter but they did not return the favour by stopping TTP from attacking Pakistani civilians and soldiers. This contradiction is going to get worse … In my opinion, we will now see an escalation in TTP’s war against Pakistan.”

Though Pakistan has downplayed its influence over the Taliban, internationally the country is paying a price for its apparent tolerance of the group. Senator Mustafa Nawaz Khokhar told the Guardian that perceived support of the Taliban had isolated Pakistan at the UN as well as proving to be a diplomatic failure. “If we are seen to align ourselves with a regressive force then we will be doing a great injustice not only to the people of Afghanistan but even Pakistan,” said Khokhar.

US-Pakistan relations, long in tatters, had also been further soured by US belief that Pakistan should “do more” to use its leverage with the Taliban to ensure peace in Afghanistan.

The Pashtun Tahafuz Movement (PTM), a social movement for the human rights of the Pashtuns living in the Pakistan areas bordering Afghanistan, said it had already seen an escalation in target killings, extortion and kidnappings carried out by the Afghan Taliban in Pakistan’s border areas.

Mohsin Dawar, a leader of the PTM, said: “The more momentum that Taliban gain in Afghanistan, the greater the consequences that will faced by Pakistan. TTP and Taliban have the same ideology and won’t ever separate from each other.”

Dawar added: “When this religious militancy, the seed of which has been sowed by Pakistan, heads towards Pakistan, it will be catastrophic.”