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Police in Australia on Wednesday announced they arrested two people over plans to carry out a terror attack in Sydney, linking the raids to an earlier counterterrorism operation last December, The Wall Street Journal reported.

Australia’s Federal Police and its state counterparts said they had arrested a 15-year-old teenager and a 20-year-old man, while three men already in prison on terrorism offenses would face court on Thursday over involvement in the plan.

“As a result of search warrants executed last December, as well as numerous amounts of electronic and physical surveillance, has today culminated in what we believe sufficient evidence to be able to charge two individuals with conspiracy to prepare for a terrorism attack,” Federal Police Deputy Commissioner Michael Phelan was quoted as having told journalists in Sydney.

Police last year arrested several men after raids that uncovered documents designed to facilitate a terrorist attack, possibly on police headquarters in Sydney or on a random civilian in the city.

The latest raids, according to The Wall Street Journal, were on homes in the same areas of southwest Sydney. In September last year, more than 800 police and intelligence agents carried out raids in Sydney and the northeastern city of Brisbane, detaining 15 people.

ISIS terrorism and radicalization have been on the rise in Australia over the past two years, with police in September of 2014 arresting 15 terror suspects of an ISIS cell that was planning to behead a random member of the public in a campaign of terror.

Last December, Sydney was rocked by a siege at cafe by Iranian-born Man Haron Monis, a self-styled cleric with a history of extremist views.

He took 17 people hostage for some 16 hours, with the siege ending after Monis shot dead cafe manager Tori Johnson, prompting police to storm the building and kill him. Another hostage died in the crossfire.