Britain and four key security partners are to boost intelligence-sharing on known or suspected terrorists.
The “Five Eyes” countries have signed a “statement of intent” to enhance the exchange of information held on critical watchlists.
Following talks between senior ministers, the alliance also called on the technology industry to do more to tackle illegal content online and highlighted the danger of security services being left in the dark by advanced encryption.
Home Secretary Sajid Javid and counterparts from Australia, Canada, New Zealand and the USA thrashed out a string of commitments during the two-day summit on Australia’s Gold Coast.
An official communique published after the meeting said globalised terrorist networks and violent extremists “pose a real and unabating threat to our communities”.
The ministers noted that ongoing efforts to dismantle terrorist groups in the Middle East have created new risks, as foreign fighters return to their countries of origin or move to other regions.
“We committed to the expanded sharing of information about known or suspected terrorists between our national security and border protection agencies, reiterating that the detection of international movements of terrorists and their associates relies on the rapid sharing of information between partners,” the document said.
“We reaffirmed that alerts and intelligence relating to the movement of known and suspected terrorists will be shared between all five partners quickly and effectively.”
It is understood a new working group has been proposed to spearhead the drive.
The Five Eyes partnership is seen as crucial to the UK’s efforts to counter the terrorist threat, which is seen as unprecedented after five attacks last year.
At the end of June, Britain’s security agencies were running more than 650 “live” investigations across all forms of terrorism.
MI5 and the counter-terror policing network have around 3,000 active “subjects of interest”, plus a wider pool of more than 20,000 individuals who have previously featured in inquiries.
The expansion of information-sharing with international partners follows a domestic measure announced earlier this year that will see intelligence circulated more widely in an attempt to stop suspects before attack plots can crystallise.
The Five Eyes ministers also warned that the “anonymous” and “instantaneous” nature of the online environment has magnified threats including terrorism and child sexual abuse.
Calling on the digital industry to take more responsibility for material on their platforms and applications, they said: “Just as the internet provides many benefits, it also provides opportunities for people to carry out crimes and spread illicit content.”
The communique stressed that the countries have “no interest” in weakening encryption mechanisms.
But it said: “The inability of intelligence and law enforcement agencies to lawfully access encrypted data and communications poses challenges to law enforcement agencies’ efforts to protect our communities.”
A separate “statement of principles” encouraged communication service providers to voluntarily establish “lawful access solutions”.
It added: “Should governments continue to encounter impediments to lawful access to information necessary to aid the protection of the citizens of our countries, we may pursue technological, enforcement, legislative or other measures to achieve lawful access solutions.”
Amid the heightened threat, focus has fallen on end-to-end encryption, which means messages and communications are encoded so only the sending and receiving devices can read them.
Security chiefs and senior police officers have repeatedly claimed the technology is making the task of disrupting terrorist plots and child abuse more difficult.
In other commitments, the alliance announced that a new group will be formed to improve information-sharing on emerging threats in the aviation sector and committed to working collectively to confront activity of “hostile states”.
Mr Javid said: “The historic Five Eyes security partnership is absolutely vital in tackling the shared international threats we all face, and the UK will continue to play a leading role.
“Our ongoing cooperation and the commitments made at the summit will ensure we have the strongest approach possible when it comes to combatting those who seek to undermine our national security.
“Our united, unwavering response is crucial.”