ONE of two schoolboys ­arrested yesterday as they were allegedly preparing to behead someone in Sydney’s southwest is related to a convicted terrorist.

Police swooped on the 16-year-olds in a laneway behind a Bankstown mosque about midday, hours after the pair allegedly bought two bayonets at a gun shop.

The pair were taken to Bankstown Police Station where they were questioned into the night before being transferred to Cobham Juvenile Justice Centre at St Marys.

Both were this morning charged with terror related offences and will appear in Parramatta Children’s Court later today.

The threat of an attack was considered imminent and police wearing protective vests descended on the prayer hall after officers received information about the alleged purchase of the knives.

The pair allegedly also had pieces of paper with religious statements written on them that were to be read out while they carried out a beheading.

It is understood police were examining the documents to see if they contained information on who was to be targeted in the beheading.

Police said speculation the pair were heading for nearby Bankstown police station had not been established.

One boy was known to counter-terrorism police as a teenage radical after he gained notoriety when he refused to stand for the national anthem as a schoolboy at East Hills High School last year.

His home was raided during the September 2014 Operation Appleby raids, Australia’s largest counter-terrorism operation to date.

The boy’s relative has been convicted on terror-related offences.

One of the boys, from Greenacre, is being represented by leading criminal lawyer Omar Juweinat, who was last night with his client.

“This is a sensitive time, not only politically but also for this young man’s family who are shocked to hear about their son’s arrest,” he said.

He would not comment on the allegations being made against his client.

It is understood that the arrests came as part of a continuing counter-terrorism investigation.

In a bizarre twist, soon after the arrests radical Muslim preacher Junaid Thorne appeared in the street and demanded police tell him, “Where are my brothers?”

Thorne, 27, is a known political radical who spent four months in Goulburn’s Supermax jail last year for trying to evade counter-terrorism authorities by flying from Perth to Sydney using a false name.

Outside Bankstown police station, a family member of one of the boys queried whether the pair had been armed with knives.

The 17-year-old, who was accompanied by his mother, said the family had not yet been allowed to see his sibling.

“I don’t know if they had knives, that’s what they’re claiming, but we’re trying to confirm,” the boy said. “It’s a very hard time for us.”

The mother of one of the boys was asked what the teens were doing when they were picked up by authorities. “Nothing happen. He go fishing and nothing happened,” the woman told Nine News.

One of the accused is linked on social media to another well-known political extremist, Wissam Haddad.

Terrorism expert Professor Greg Barton from Deaken University said it appeared authorities had been tracking the boys for some time.

“They had sufficient concerns. That is unusual, to be putting police resources on young teenagers, but clearly there is a longer back story here,” he told Nine Network.