SYDNEY, Australia - Australia and New Zealand warned on Thursday that extremists may be planning an attack on the commemoration of a First World War campaign that is being held in Turkey this month.

Australian Veterans Affairs Minister Dan Tehan urged the nearly 500 Australians and New Zealanders registered to travel to Gallipoli, Turkey, to mark ANZAC Day on April 25 to exercise a high degree of caution amid the warning, but offered no specifics about the alleged threat. ANZAC Day is an annual holiday commemorating the April 25, 1915, landings in Gallipoli - the first major military action fought by the Australian and New Zealand Army Corps during the First World War.

Australian Federal Police deputy commissioner Mike Phelan declined to release details of what prompted the warning, saying only that the government had received information that extremists may attack the services being held on the Gallipoli peninsula. Phelan said there was no specific plot linked to the alert.

"It is just that terrorists may indeed try to carry out a terrorist attack during the celebrations," Phelan told reporters in the nation's capital, Canberra. "That is all we have got at this stage."

Tehan said Australia and New Zealand were working closely with Turkish authorities on security arrangements and the commemoration was scheduled to continue as planned.

For the past two years, Australian police have said they thwarted planned attacks on ANZAC Day celebrations in Australia. In 2015, police in Melbourne arrested five teenagers on suspicion of plotting an Islamic State group-inspired attack intended to coincide with the city's ANZAC service. In 2016, police arrested a 16-year-old and charged him with planning an attack on an ANZAC ceremony in Sydney.

New Zealand Foreign Minister Murray McCully said he could not be more specific about the nature of the threat or where the information had come from. He said he'd been getting advice about it over the last day or two.

McCully urged travellers to Gallipoli to regularly check the government travel website for updates. He said he had confidence in how Turkish authorities were handling security, and apologized for not being able to offer more information.

"It's not an area in which they encourage ministers to let their imaginations wander," he said. "We very carefully have to follow the steps and script of the officials who give advice in this area."

Many New Zealanders feel a strong bond with Gallipoli, McCully said.

"The fact that so many New Zealanders go to Gallipoli at this time of year speaks volumes about the significance it holds," he said.

-----

Associated Press writer Nick Perry in Wellington, New Zealand, contributed to this report