Vin Diesel says 'Fast & Furious 7' was the ''hardest movie'' he's ever made.

Filming has now wrapped for the seventh instalment of the film franchise and actor Vin Diesel has opened up about the pain of losing his co-star Paul Walker in a tragic car accident in late 2013.

Talking to Access Hollywood, Vin reflected: ''It was surreal. Needless to say the hardest movie I've ever done.

''I remember when the tragedy happened. My mother said, 'It's not fair that you have to mourn in front of the world'.

''What's even harder is to mourn and simultaneously pretend that that person is next to you. It's very, very weird.''

Paul - who played Brian O'Conner in the films - died in November last year while in the passenger seat of a car being driven by his friend Roger Rodas.

The car burst into flames after hitting a lamppost in California and it's thought that the vehicle could have been travelling at up to 100 miles per hour.

Sadly, Paul died before finishing filming his scenes for 'Fast & Furious 7' and his brothers Caleb and Cody Walker were asked to fill in for their late sibling as a body double, so that the movie could be completed.

Dwayne ''The Rock'' Johnson - who also stars in the film - previously confessed that completing the project was ''bittersweet''.

He shared: ''Last day on set, it was bittersweet. It was emotional, it was beautiful. It was amazing, it was sad, it was all those things. We are all in the business we all know and love Paul Walker and we truly lost one of the good ones.''

He added: ''My number one thought is for his daughter [Meadow Walker]. I believe she is doing okay. I think she's doing as okay as she can.''

Wow, that's really sad to hear.