Police have arrested a man on terrorism charges from the same part of Cardiff as the two Isis jihadists who made a blood-curdling terrorist propaganda video.
Officers held an 18-year-old in Grangetown on 2 July.
It happened close to the homes of Isis terrorists Retaad Khan and Nasser Muthana, both 20.
A spokesman for South Wales Police said: "He has been arrested under the Section 5, Terrorism Act 2006 for assisting in the preparation of an act of terrorism."
WalesOnline reported that a link between the arrested teenager and the homegrown jihadists Khan and Muthana has not been ruled out by police. Police have only said that the arrest is not related to Khan and Muthana directly.
The pair caused alarm by appearing in a video calling upon other Muslims to lay down their lives in Iraq and Syria to create a Shariah state founded upon harsh Islamic laws.
Muthana has appeared on social media with an image of homemade bombs mocking concerns raised in Britain that British-born terrorists currently in Iraq could pose a security risk as and when they return to the UK.
Beneath an image of bombs in metal containers, Muthana crowed: "So the UK is afraid I come back with the skills I've gained."