Clinical Ireland see off Scots in Yokohama drizzle in Rugby World Cup

Forwards James Ryan, Rory Best and Tadhg Furlong all smashed over in the first 25 minutes and winger Andrew Conway secured the bonus point with the fourth try in the second half, with a single Greig Laidlaw penalty all Scotland had to show.

There was some concern that injury-prone flyhalf Johnny Sexton gave up kicking duties early on, and flanker Peter O'Mahony and centre Bundee Aki left early with head injuries, but coach Joe Schmidt said Sexton was fine and that the other two were symptom-free. Scotland also lost flanker Hamish Watson to a serious-looking injury.

"I was delighted with the first half, I think we really put some pressure on, defensively as well as in attack," Schmidt said in a pitchside interview.

"I think they [Scotland] are a team that will be very, very hard to bowl later in the tournament and maybe we just got them early enough that they hadn't quite hit their straps."

With the flat, unsuccessful defence of their 2018 Six Nations title still hanging over them, Ireland were desperate to get up and running quickly in Japan and did exactly that as the three early tries from their front five put them in total control.

Encouragingly for Schmidt, the first two came from clean lineout ball, putting to bed some of the concerns over his team's setpiece as well as his much-debated call to leave go-to jumper and caller Devin Toner at home.

The opener on six minutes was all about the rampaging second-row pair of Iain Henderson and Ryan while the second was a simpler forwards' effort as Best followed up another accurate throw to mark his 121st test with a try.

The clear Scottish intent to test the aerial skills of the relatively inexperienced back three of Conway, Jordan Larmour and Jacob Stockdale - forced upon Schmidt by minor injuries to Keith Earls and Rob Kearney - led to a couple of errors and helped Laidlaw get them on the board.

But it was all too easy for the Irish pack, which can be unstoppable under Schmidt if allowed to recycle possession as Furlong made it three tries from three forays into their opponents' 22 metres.

The long-threatened rain held off until late into the first half, only tightening Ireland's stranglehold on the game with the disappointing Scots unable to trouble a very well-organised Irish defence.

The slippery surface ended the game as a spectacle, not that it mattered to the sea of green around Yokohama's International Stadium as the travelling Irish fans drowned out the faint sound of Scottish bagpipes.

They had one more try to cheer before the end as Conway added the bonus point just before the hour.

With Ireland's impressive pack likely to have too much in six days time for a Japanese eight who were troubled up front by Russia in their opener, Schmidt can effectively already start to prepare for an expected quarter-final against South Africa.

The consolation prize for Scotland, if they can negotiate their way out of the pool, will almost certainly be a last eight encounter with holders New Zealand.

"We didn't start with the energy, accuracy and aggression needed to beat Ireland," Scotland coach Gregor Townsend told a news conference.

"When you give them a 15-20 point start, it is hard to come back."