Dan Tehan, Australia’s veterans affairs minister, said the government received intelligence that “terrorists may seek to target Anzac Day commemorations on the Gallipoli Peninsula”.
He said Turkish authorities were aware and providing a high level of protection, urging visitors to minimise time in Istanbul and Ankara, while avoiding large crowds and tourist sites.
“The Australian Government does not provide this advice lightly,” Mr Tehan added.
“In the current global environment, major events attract threats of varying degrees of credibility. Regrettably Anzac Day is not immune.”
Almost 500 Australians and New Zealanders have registered to travel to Gallipoli to mark Anzac day on 25 April, which commemorates the deaths of thousands of soldiers in the first major military action fought by the two countries’ corps in 1915.
Mike Phelan, deputy commissioner of the Australian Federal Police, declined to release details of what prompted the warning, saying 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,” he told reporters in Canberra. “That is all we have got at this stage.”
New Zealand’s foreign minister, Murray McCully, said he could not be more specific about the nature of the threat or where the information had come from.
“We very carefully have to follow the steps and script of the officials who give advice in this area,” he added.
“The fact that so many New Zealanders go to Gallipoli at this time of year speaks volumes about the significance it holds.”
Authorities did not name any terrorist groups in relation to the threat but suspicion turned to Isis after two previous Anzac Day plots by the group’s supporters were thwarted.
A boy who was 16 at the time pleaded guilty to planning an attack on the occasion in Australia last month, after Sydney police found he tried to obtain a gun and bomb-making instructions in 2016.
Separately, a 15-year-old British boy was sentenced to life in prison for plotting to behead police officers at an Anzac Day parade in Melbourne in 2015.
Turkey has been hit by a wave of terror attacks by Isis and Kurdish militant groups, mainly targeting Istanbul, Ankara, security forces and cities near the Syrian border.
The Foreign and Commonwealth Office’s travel advice warns of a high risk of terrorism throughout Turkey, saying that “further attacks are likely and could be indiscriminate”.
“Attacks are most likely to target the Turkish state, civilians and demonstrations,” the advice states.
“Nevertheless, it’s likely that some attacks will also target western interests and tourists from western countries, particularly in the major cities."
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