CANBERRA, Australia (AP) — Australian police disrupted a plot to bring down an airplane and arrested four men in raids on homes in several Sydney suburbs, the prime minister said Sunday. Prime Minister Malcolm Turnbull said that security has been increased at Sydney Airport since Thursday because of the plot. The increased security measures also were extended to all major international and domestic terminals around Australia overnight. "I can report last night that there has been a major joint counterterrorism operation to disrupt a terrorist plot to bring down an airplane," Turnbull told reporters.