Gregor Townsend says facing title-chasing France in the Six Nations in Paris on Saturday is "probably the biggest challenge right now in world rugby".

The French put in a stunning display to thrash Ireland in round four as the Scots held off a late Wales fightback to secure a bonus-point win of their own at Murrayfield.

That victory in Dublin has put France in the box seat, knowing any victory over the Scots at the Stade de France will see them win the championship.

"I think when you put all the factors together, the French team at home are always a huge challenge," said Townsend.

"The way they're playing, even in their defeat they scored a lot of points and could have scored a number more at Twickenham.

"They're playing a game of rugby that's really producing points and scores. They're physical, they're bringing a fresh pack on at some stage in the second half and they're going for the title.

"It's a great game to go up against one of the best teams in the world at home."