Melbourne’s long-awaited $12.6 billion Metro Tunnel has moved a step closer to opening, with the first trains testing out the infrastructure.

Trains ran in each of twin nine-kilometre tunnels underneath central Melbourne from South Yarra to Anzac Station overnight, marking the start of project testing.

The trains travelled at between 5km/h and 25km/h for the test.

Victorian Premier Daniel Andrews toured the new Anzac Station on Tuesday and denied the project was over-budget.

“It’s been delivered against the budget that’s been allocated,” he said.

The Metro Tunnel is expected to open in 2025. Along with Anzac, it has four other stations – at North Melbourne, Parkville, State Library, Town Hall – that will take three busy train lines out of Melbourne’s congested City Loop.

– with AAP