Police have arrested a teenager said to have been planning to launch an "imminent" lone terrorist attack in Sydney, Australia.
The 18-year-old was expected to be charged with planning a terrorist attack, the Australian Federal Police said.
They said another charge - preparing to enter a foreign country to engage in hostile activities - was expected to be filed in connection with an earlier attempt by the teenager to travel to Syria.
If convicted, he could face a maximum sentence of life in prison.
"The planning was occurring now and we would say that an attack was probably imminent," New South Wales Police deputy commissioner Catherine Burn said.
The suspect had been making arrangements to obtain a firearm, Australian Federal Police acting deputy commissioner Neil Gaughan said.
Officials believe he was working alone and his arrest meant there was no longer any threat to public safety linked to the alleged plot, he added.
Ms Burn and Mr Gaughan would not say what the alleged plans involved, including the proposed targets.
The suspect, who had been on the authorities' radar since last year, was stopped at Sydney airport in February when he attempted to travel to Syria, Mr Gaughan said.
His passport had been cancelled and he was prevented from leaving the country.
Since then, he had been under police surveillance, attorney general George Brandis said.
Australia's government raised the country's terror threat level in 2014 in response to the domestic threat posed by supporters of the Islamic State group.
Police have since conducted dozens of raids they say have been aimed at thwarting multiple terror plots around Australia, including an alleged plan to attack government buildings and a naval base in Sydney.
Many of those arrested have been teenagers, including a 16-year-old who was charged with plotting a terrorist attack on an Australian Veteran's Day ceremony in April.
"We are still seeing people planning and preparing for such attacks and unfortunately, that group of people are getting younger and younger," Ms Burn said.