A security scare at Melbourne Airport has forced hundreds of passengers out of the Qantas terminal, delaying several flights.

An emergency evacuation of the terminal was ordered just after 7.15pm on Sunday when someone entered the terminal through an exit, a Qantas spokesman said.

"As a result, we had to evacuate the entire terminal, so everyone could be rescreened by security," he said.

It took more than an hour to send everyone through security for a second time.

At least five domestic flights were delayed due to the security scare, he said.