Ireland continued their winning start to the World Cup with a bonus-point victory over Tonga on a landmark night for Johnny Sexton in Nantes.

Sexton added a fourth to surpass Ronan O'Gara as Ireland's record scorer.

Vaea Fifita scored for Tonga before half-time but James Lowe, Bundee Aki - with two - and Rob Herring capped another resounding Ireland win.

While the Irish encountered more headaches here than they did in their 12-try destruction of Romania, Andy Farrell will be pleased that his side moved on to 10 points before next week's eagerly anticipated encounter with holders South Africa in Paris.

Crucially, the world's number one-ranked team again appeared to avoid injuries to key players with Farrell even afforded the luxury of ending Sexton's night at half-time after the out-half's record-breaking contribution.

Tonga, who did not play last week, will look to bounce back when they take on Scotland in Nice on Sunday week.

Sexton breaks O'Gara's record

Having watched his side blow away Romania in their opening match last week, Ireland head coach Andy Farrell recognised the threat posed by Tonga by naming a near full-strength team.

And while Tonga, who had four former All Blacks in their line-up, represented a clear step-up in quality from Romania, the Irish quelled their opponents' early energy to secure the bonus point before half-time.

Sexton was, once again, instrumental to an Ireland win. The 38-year-old, who will retire after the World Cup, ended the night on a career total of 1,090 points, seven clear of O'Gara, before being hooked at the break with his job done and the bonus point in the bag.

"I don't think it is about individual achievements this evening," Sexton said after the game.

"It is about getting the next win and keep building in this tournament. It's week-on-week in a World Cup and you have got to produce it week after week."

While Tonga impressed early on, by the time Sexton dotted down to bag Ireland's bonus point, it only looked like being a 15th straight win for Farrell's side.

Ireland get job done before Boks showdown

Ultimately, Ireland just had too much for the 15th-ranked team in the world.

With Sexton and William Havili having exchanged early penalties, Ireland prop Andrew Porter had an opener ruled out by the television match official (TMO) for Hansen's knock-on.

Ireland were not forced to wait long, however, as Beirne broke Tonga's early resistance. The Munster lock, who scored twice against Romania, stretched to touch down under the posts, wrapping up a move that was started by Sexton's switch of play.

Havili's second penalty reduced the deficit to four but Ireland were gifted a second try, with Doris going over after Solomone Kata's foul on James Lowe handed the Grand Slam winners a penalty deep inside the Tongan 22.

If Ireland's second was down to Tonga's indiscipline, their third was a product of Hansen's winged wizardry. After collecting a Keenan pass, the Connacht wing danced through a sea of red jerseys and moved the Irish further clear.

And while Ronan Kelleher failed to ground the ball, Ireland's captain soon delivered the bonus point as he slipped through the Tongan defence to score his third try of the tournament and move past O'Gara's mark of 1,083 points, and added the conversion before he was replaced by Ross Byrne at half-time.

Undeterred, Tonga finished the half strongly. After Ireland flanker Peter O'Mahony was sin-binned, the Pacific Islanders piled on the pressure before Fifita crossed.

Unfortunately for Tonga, they were unable to build on a rousing end to the first period, but while they began to show signs of fatigue, Ireland's insatiable appetite for tries shone through.

First, Lowe dived over following a maul before the in-form Aki emulated his double against Romania to continue his exceptional start to the tournament.

Then Herring - who was earlier denied a try by the officials - wrapped up victory for Ireland, for whom it was another job well done.

Ireland can enjoy a rest on Sunday before focus switches to Saturday's heavyweight showdown with three-time champions South Africa at the Stade de France.

'Best still to come from relentless Ireland' - analysis

Former Ireland flanker Chris Henry on BBC Radio Ulster: "That's a pretty awesome result. Ireland are just so ruthless and relentless.

"Tonga, we knew they were gong to put up a fight but still the score line is incredible and everything is still just pointing in the right direction for this Irish team and it's a pleasure to watch them at the moment.

"The key thing is that Sexton got another great 40 minutes and there's a lot of positives. The best is yet to come from this Irish team."

Teams

Ireland: Keenan; Hansen, Ringrose, Aki, Lowe; Sexton (capt), Murray; Porter, Kelleher, Furlong, Beirne, Ryan, O'Mahony, Van der Flier, Doris.

Replacements: Herring, Kilcoyne, Bealham, Henderson, Baird, Casey, Byrne, Henshaw.

Sin-bin: O'Mahony (40+3)

Tonga: Piutau; Taumoepeau, Fekitoa, Ahki, Kata; Havili, Pulu; Fisi'ihoi, Ngauamo, Tameifuna (capt); Lousi, Fifita; Halaifonua, Talitui, Fifita

Replacements: Moli, Koloamatangi, Apikotoa, Paea, Funaki, Vailanu, Takulula, Inisi.

Referee: Wayne Barnes