SYDNEY (AP) — Counterterrorism raids in Sydney on Thursday were sparked by security intelligence that the Islamic State movement was planning a random, violent attack in Australia as a demonstration of its reach, the prime minister said. Australian police detained 15 people and raided more than a dozen properties across Sydney in the country's largest counterterrorism operation, saying intelligence indicated an attack was being planned on Australian soil. Police have issued an arrest warrant for a former Sydney nightclub bouncer, Mohammad Ali Baryalei, 33, who is suspected to be Australia's most senior member of the Islamic State group. About 800 federal and state police officers were involved in the Sydney operation — the largest in Australian history, Federal Police Deputy Commissioner Andrew Colvin said. The arrests come just days after the country raised its terror warning to the second-highest level in response to the domestic threat posed by supporters of the Islamic State group. Last week, Australian police arrested two men in Brisbane for allegedly preparing to fight in Syria, recruiting jihadists and raising money for the al-Qaida offshoot group Jabhat al-Nusra, also known as the Nusra Front. The government has said it believes about 100 Australians are actively supporting extremist groups from within Australia, recruiting fighters and grooming suicide bomber candidates as well as providing funds and equipment.