Police have ramped up security at Australian airports after foiling what they described as a credible and “elaborate” plan to detonate a bomb on a plane.

Tougher security has now been implemented at Australian airports, including additional screening of bags, and police say the current counter-terrorism operation may last days.

The four men arrested in raids on five properties in the Sydney suburbs of Surry Hills, Lakemba, Wiley Park and Punchbowl on Saturday night have not yet been charged.

The Australian federal police commissioner, Andrew Colvin, said a tip-off from partner agencies led to the raids on Saturday night. He said the terrorist attack planned to use an “improvised device” to target an Australian plane.

He said the threat was credible, adding: “We believe it’s Islamic-inspired terrorism. Exactly what is behind this is something we need to investigate fully.”

Prime minister Malcolm Turnbull said the foiled operation was not a lone wolf-style attack. “We face a range of terrorist threats, some of them are lone actors, who activate very quickly, with very little warning,” Turnbull said on Sunday. “On other occasions, you get quite elaborate conspiracies. This appears to be in that category.”

The attack was to target the Australian aviation industry at a major airport, police said. Colvin said there was no evidence that security at Australian airports had been compromised. “Terrorists are becoming very ingenius about ways to defeat our security mechanisms,” he said.

“Australia has some of the best, if not the best airport security arrangements in the world and we’re confident those measures are effective, and would have been effective, in this circumstance.”

The searches in Sydney will continue in coming days. Police said a “number of items of great interest” have been seized.

The Seven Network reported a suspicious device was found in a Surry Hills terrace, which was raided by 40 riot squad officers on Saturday.

TV footage showed a man with a bandage on his head and draped in a blanket being led away by authorities.

A neighbour described the family who lived in the house in Cleveland Street as “perfectly nice and normal people”.

“We knew them to say hello to and they seemed nice,” the woman, who didn’t want to be identified, told AAP.

Colvin would not say whether the four men were on a terror watch list.

Turnbull said the additional security and screening measures at Australian airports may cause delays to travellers. “More bags will be checked, it’s really intensifying what we’re already doing,” he said. And that will be, some of that will be visible, some of it will not be visible.”

Virgin Australia issued a statement advising passengers to arrive at the airport two hours before a domestic flight and three hours before an international flight. Virgin also asked passengers to limit carry-on baggage where possible.

“The travelling public can expect to experience an increased level of security scrutiny at the airport but they should not be concerned about these precautionary measures,” the airline’s statement said.

“As the measures place an additional burden on the screening system, it may take a little longer than usual to get through the process.”

The prime minister said he was being briefed on the operation’s progress by security agencies.

Australia’s national terrorism threat advisory system lists the threat level as “probable”, and Turnbull said that would not change immediately.

NSW police commissioner, Mick Fuller, said police may have waited another week before raiding the homes, had it not been terror-related. “The reality with terrorism, you can’t wait till you put the whole puzzle together. If you get it wrong, the consequences are severe.

“We risk assess regularly, around the clock, and you need to make a decision at some stage when it the right time to go. Both Australian Federal Police and New South Wales police agreed last night was the right time to go.”

Justice minister, Michael Keenan, said the foiled plot was the 13th significant counter-terrorism disruption in Australia.