A lockdown at an Ayrshire hospital has been lifted after police were called to a “serious incident” following reports of a stabbing at the site and another two “potentially linked” incidents in the area.

Crosshouse hospital in Kilmarnock was placed under lockdown for about three hours and ambulances were diverted to University Hospital Ayr while officers dealt with the first incident. It is not currently known who has been injured.

Police said they were also dealing with a second incident in Portland Street in the centre of Kilmarnock, about two miles from the hospital. Part of the town centre at the railway viaduct has been closed to traffic and the public were asked to avoid both areas.

A third incident, a “serious road crash” on the A76, was also being attended by police.

The incidents are not being treated as terror-related. Police Scotland said inquiries were at an early stage and that the areas involved have been cordoned off. The force added that there was no cause for concern to the wider community.

In a statement on Twitter, the force said: “Police Scotland is currently dealing with 3 potentially linked incidents in the Kilmarnock area. The first occurred around 7.45pm outside Crosshouse Hospital, the second around 20 minutes later on Portland Street, and the third, a serious road crash, on the A76, around 8.30pm.”

It was confirmed just before 11pm that the hospital lockdown had been lifted.

The first minister, Nicola Sturgeon, tweeted: “My thoughts are with those involved in these very serious incidents in Crosshouse/Kilmarnock. Please help @AyrshirePolice do their job by following the advice to stay away from the areas affected.”

The Scottish justice secretary, Humza Yousaf, described the hospital incident as “very serious” and urged people to follow police advice and avoid both areas.

Dr Crawford McGuffie, the medical director of NHS Ayrshire and Arran, said said police had confirmed that the risk to patients, staff and visitors to the hospital was minimal.

He added: “There remains a large police presence on the grounds of the hospital.

“We would like to reassure anyone coming to the hospital, in particular to any patients or staff coming on shift, that Police Scotland have confirmed it is safe to do so. However, if you are worried, please speak to the on-site Police Scotland officers.

“As this is a Police Scotland incident, we are unable to comment any further at this time.”