Police in Britain said Monday they have arrested a 14-year-old boy in connection with an alleged Islamic State-inspired attack plan in Australia.
The boy was arrested Saturday "on suspicion of being concerned in the commission, preparation or instigation of acts of terrorism and remains in police custody for questioning," Greater Manchester Police in northwest England said in a statement.
Australian police arrested five men in counterterrorism raids in Melbourne on Saturday and charged one of them with conspiring to commit a terrorist act on Anzac Day on April 25, when ceremonies are held to remember Australian and New Zealand Army Corps troops who fell in the World War I Gallipoli campaign.
One of the officers working on the case in Britain, Detective Chief Superintendent Tony Mole, said: "We have uncovered communication between an individual in the northwest and a man in Australia to what we believe is a credible terrorist threat.
"As soon as this information came to light we acted quickly with the relevant authorities here and abroad."
Police said the boy, from Blackburn in Lancashire, northwest England, had previously been arrested on April 2.
Authorities stressed they had not uncovered any evidence of an imminent attack being planned in Britain.
Australian police said the arrest in Britain was connected to their operation.
"Victoria Police and the Australian Federal Police can confirm a link between the arrest of a 14-year-old boy in Blackburn, Lancashire in the United Kingdom on Saturday with Operation Rising," the state and national police forces said in a joint statement.
"Investigators received information from U.K. authorities after they allegedly uncovered communications between the teenager and a man in Australia.
"The nature of the communication will form part of the investigation."
Of the five men arrested in Melbourne on Saturday, Sevdet Besim, 18, remains in custody charged with conspiring to commit a terrorist act.
Another 18-year-old, who has not been named, is being held without charge on an interim preventative detention order.
Two other men, aged 18 and 19, have been released pending further inquiries while another 18-year-old was released but is facing weapons offenses.
After the arrests in Australia, police in Britain said they were examining the security measures at events.
"We already have protective security plans in place for major Anzac events in the U.K. but as a sensible precaution all forces have been asked to review security arrangements at related events," said Scotland Yard's Assistant Deputy Commissioner Neil Basu.
It is understood that the review covers Anzac Day events but also commemorations for the 70th anniversary of VE Day on May 8 being attended by high-profile figures including members of the royal family.