The truck's 44-year-old driver was also injured and had to be taken to hospital. Territory and Municipal Services took charge of the welfare of the animals when they arrived.

TAMS counted 505 sheep on the truck, and said about 150 had to be euthanised.

The area is no stranger to sheep deaths.

Last August, more than 100 sheep were killed after a truck carrying about 400 animals rolled at the roundabout of Johnson Drive and Monaro Highway at Calwell.

After that accident a truck driver said the Monaro Highway roundabout was a 'wild' area and difficult to navigate for trucks.

Emergency services were called to the rollover near the new ACT Fire & Rescue Station just after 2pm.

The driver was negotiating the roundabout when the multi-layered truck tumbled.

The spokesman said local vets responded to the incident, and assisted in euthanising injured sheep as police and territory and municipal services arrived. TAMS were unable to say which company the truck belonged to or where it was heading.

All sheep had been taken out as of 4.30pm and were being assessed.

An ACT Policing spokesman said northbound traffic heading towards the Drakeford Drive and Tharwa Drive roundabout was diverted onto Mentone View in Conder.

Traffic was also blocked from turning right at the Tharwa Drive roundabout towards Theodore.

The spokesman said no other vehicles were involved.