A statue of St Barbara, protector of miners stands in the NEAT Gotthard Base Tunnel during its official opening. [Photo/Agencies]

The first travellers through the tunnel were 500 lucky winners plus guests who entered a lottery for the trip.

The overall project includes the Loetschberg rail tunnel that has already opened, the Ceneri tunnel still being built and renovations to make rail tunnels at least 4 metres high at the corners to be able to handle big freight containers.

Swiss work is due to end in 2020, but Italy and above all Germany have lagged on infrastructure improvements on the route, something Merkel said on Wednesday she would address.

($1 = 0.9928 Swiss francs)