Australia conducted a major counterterrorism sweep across Sydney in a major effort to foil a random attack on the country, with 15 people detained by police on Thursday.

The anti-terror raid is the biggest so far in the history of Australia, according to Federal Police Deputy Commissioner Andrew Colvin. Around 800 police officers conducted operations in several properties in Sydney and eastern region of Brisbane and Logan, Chron reported.

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The police raids last week centered on a Muslim book store and a community center in Logan.

The 15 people were arrested a few days after Australia elevated its terror warning from "medium" to "high," the second-highest response level to local threat posed by Islamic State of Iraq and the Levant (ISIL) supporters.

Authorities believe the suspects intended to commit random terror acts in the country, Colvin explained. The operation was part of police efforts to foil the acts of violence against the public at an early stage, the deputy commissioner added.

Both Colvin and the police declined to disclose the charges filed against the suspects and other details about their alleged terror plot. However, one person was reportedly set to appear in court on Thursday over serious terrorism charges.

Last week, police apprehended two suspects in Brisbane for allegedly raising funds and recruiting members for Al Qaeda-linked jihadist group Nusra Front, and preparing to join the battle in Syria. The Brisbane raids on Thursday came as a follow up to the previous anti-terror sweep, Colvin said.

Terrorism threat in Australia has been steadily rising over the last year because of some Australians have been convinced to join the ISIL fight in Syria and Iraq, according to David Irvine, Director-General of Australian Security Intelligence Organization.

When Prime Minister Tony Abbott announced the heightened threat response level, he noted that there was no intelligence that suggested an imminent violent attack on the nation.

However, Australia is treading carefully as an estimated 60 citizens have been reportedly fighting for ISIL and the Nusra Front in the Middle East, the report said.

The government also believes there are around a hundred Australians backing the Islamist groups from within the country by recruiting members, training new suicide bombers and providing them with funds and materials.

TagsAustralia, counterterrorism raids, ISIL, Nusra Front, jihadists