India spinner Ravindra Jadeja on Sunday said victory over a "big side" like Australia has given the team more confidence at the start of the World Cup.

The hosts defeated five-time winners Australia by six wickets at Chennai in both teams' first match of the tournament.

Jadeja's 3-28 off his left-arm spin helped dismiss Australia for 199, a total India achieved with 52 balls to spare but only after top-order wobble when they lost three wickets for just two runs.

"It feels nice to beat a big side and the confidence is good," Jadeja told reporters.

"To beat Australia, and there are few other good sides in the World Cup, to beat them is good. I will not say that things would be easy against others but if you win against three, four big teams then the confidence is different."

Australia elected to bat first in hot and humid conditions but lost an early wicket before David Warner (41) and Steve Smith (46) rebuilt the innings.

India's spinners hit back with Kuldeep Yadav sending back the left-handed Warner and Jadeja then bowling Smith with a delivery that pitched and turned from the right-hander.

"From then onwards it was not easy to come and rotate the strike for the new batters," Jadeja said of the Smith dismissal.

"I think that wicket was the turning point. So from there they were 110-3 to 199 all out."

Jadeja was ably supported by fellow spinners Kuldeep (2-42) and Ravichandran Ashwin (1-34).

Asked on the spin trio playing different roles for the team, Jadeja said it was just about getting wickets on a pitch that offered turn.

"There is no specific role. It was about getting as many wickets as quickly as we could," Jadeja said with a laugh.

Virat Kohli (85) and KL Rahul (97 not out) led the chase in a stand of 165 after India lost three of their batsmen for ducks including skipper Rohit Sharma.

"Three wickets down, there was panic. But we know Virat and Rahul, they have been doing this for the team since so many years," said Jadeja.

"They payed brilliantly. They knew the conditions well. It was amazing to see."