Spectators attending the Irish Open at Trump International Golf Links in Doonbeg, Co Clare, will face significant security checks in an attempt to ensure no weapons or sinister items are brought on to the course while the US president is present.

Precautions for what one source described as one of the “most complex” security operations to ever be take place in the State are expected to include signal jammers, which disrupt the use of drones and other devices.

Instructions issued by An Garda Síochána on Monday to the tens of thousands of people expected to travel to the golf tournament later this week include advice not to rely on satnavs in their vehicles due to road closures.

US military Chinook helicopters were spotted in the sky over Dublin on Monday, flying from the UK towards the Irish Air Corps base at Baldonnel. It is understood they were transporting equipment for the US side of the security operation surrounding Trump’s visits to Dublin and Doonbeg.

About 4,000 Irish and US security personnel, including from the Garda, Defence Forces and US Secret Service, are expected to be deployed, mainly in Clare and Dublin, according to sources familiar with the operation. This includes about 1,000 US personnel and 3,000 Irish, mainly from the Garda.