In another sign of the Middle East-based Islamic State’s expanding influence, the chief spokesman for the Pakistani Taliban and five regional commanders declared allegiance Tuesday to the group and its chief, Abu Bakr al-Baghdadi.

The announcement marked the first instance of a major contingent of Taliban figures signaling a renouncement of fealty to the Afghan Taliban’s supreme leader, Mohammad Omar. If additional Taliban commanders follow suit, the changing loyalties could not only weaken the Afghan Taliban but also leave Pakistan and Afghanistan more vulnerable to the sort of brutal tactics employed by the Islamic State in Iraq and Syria, analysts say.

“This is very serious and dangerous trend from Afghanistan and Pakistan, as it is a more lethal and violent militant group than even al-Qaeda and the Afghan Taliban,” said Ijaz Khattak, chairman of the international relations department at the University of Peshawar in northwest Pakistan.

In a message delivered last week, two factions of the Pakistani Taliban expressed support for the Islamic State. Later, however, the groups clarified that they were not abandoning their historical ties to Omar and the Afghan Taliban. Tuesday’s statement from the six commanders, however, left little doubt that they now view Baghdadi as their supreme leader.

“I show allegiance to the commander of faithful, Caliph Abu Bakr al-Baghdadi Qureshi al Hussaini, and will listen and obey every order of you and will follow your orders regardless of what circumstances may be,” Shahidullah Shahid, the chief spokesman for the Pakistani Taliban, said in the statement.

Shahid was unavailable to comment. But one of his close aides, who spoke on the condition of anonymity, said the commanders will continue to be part of the Pakistani Taliban. “These commanders will remain with the organization, but will also represent ISIS in Pakistan,” the official said, using an acronym for the Islamic State. “The decision came after differences developed with the Afghan Taliban. I can’t say now what are the differences, but these commanders have changed their loyalties from Mullah Omar to ISIS chief Baghdadi.”

For weeks, there have been signs that the Islamic State could gain a foothold in Pakistan, already home to more than two dozen terrorist groups. Last month, a 12-page manifesto was distributed in parts of Peshawar, inviting people to join the group.

Some Pakistanis have also traveled to Syria to fight with the Islamic State. But Pakistani military and political leaders have played down suggestions that the group could expand in their country.

Tuesday’s announcement could help the Pakistani military’s campaign against the Taliban, because it signaled the latest in a series of public divisions in the militant organization. But Khattak warned that those rifts could also make it easier for the Islamic State to recruit in Pakistan.

Khan reported from Peshawar.