A dramatic arrest has unfolded at Westfield shopping centre in Chatswood in Sydney's northern suburbs after a group of youths were allegedly seen carrying firearms, which turned out to be replicas.

A police spokeswoman said officers were called at 6pm on Wednesday following a number of reports from members of the public who believed they had seen men carrying guns in the shopping centre's food court.

When officers arrived, they arrested five male teenagers and seized five toy guns, some of which had been modified. The replica firearms will be forensically examined.