Pakistan's parliament has voted to give army chief Field Marshal Asim Munir new powers and lifetime immunity from arrest and prosecution, a move that critics say paves the way towards autocracy.

The 27th constitutional amendment, which was signed into law on Thursday, will also make significant changes to the way the country's top courts operate.

Those defending the changes say they provide clarity and administrative structure to the armed forces, while helping to ease a backlog in the courts.

Pakistan's military has long played a prominent role in the nuclear-armed country's politics - sometimes seizing power in coups, and, on other occasions, pulling levers behind the scenes.

Throughout its history, Pakistan has oscillated from more civilian autonomy to overt control under military leaders like General Pervez Musharraf and General Zia-ul-Haq. Analysts refer to the balance between civilian and military as hybrid rule.

Some see the amendment as a sign that the balance is shifting in the military's favour.  

"For me, this amendment is the latest indication, perhaps the strongest yet, that Pakistan is now experiencing not a hybrid system, but a post-hybrid system," says Michael Kugelman, director of the Wilson Center's South Asia Institute in Washington. "We're essentially looking at a situation where the civil-military imbalance is about as imbalanced as it could possibly be."

The latest amendment means that Munir, who has been army chief since November 2022, will now also oversee Pakistan's navy and air force. His field marshal title and uniform are for life and he will be given "responsibilities and duties" even after retirement determined by the president with the advice of the prime minister.

The expectation is that this will give him a prominent role in public life for as long as he is alive.

Supporters of the bill have argued it clarifies Pakistan's military command structure. Pakistan's government-operated news agency, the Associated Press of Pakistan, cited Prime Minister Shehbaz Sharif as saying that the changes were part of a broader reform agenda to ensure Pakistan's defence keeps pace with modern warfare requirements.