Wales extended their unbeaten run to eight games by crushing Tonga 74-24 at the Principality Stadium.

Warren Gatland's men overcame a brief scare when they saw an 18-point lead wiped out by the visitors, who drew level just after half-time, before Wales resumed normal service and cut loose.

An early penalty try was folowed by touchdowns for fly-half Dan Biggar, who contributed 19 points, and wing Liam Williams on his 50th Wales appearance.

But Tonga, beaten on all eight previous encounters against Wales, responded impressively through tries for locks Leva Fifita and Steve Mafi, before Saracens number eight Sione Vailanu powered over from close range.

Newcastle scrum-half Sonatane Takulua converted all three tries and kicked a penalty, but Wales pulled away during the final 30 minutes.

The hosts added tries from wing Steff Evans, scrum-half Tomos Williams, another from Liam Williams, centre Tyler Morgan, plus replacements Cory Hill, Aled Davies and Rhys Patchell, while Patchell kicked four conversions.

Wales' winning sequence is their longest since the 2004-05 season, while victory over South Africa next weekend would complete a first autumn Tests clean sweep.

Despite Gatland making 14 changes from the side that claimed a first victory for 10 years over Australia last Saturday, Wales were ultimately far too strong as they posted their highest points total since beating Namibia 81-7 during the 2011 World Cup in New Zealand.

Wales made a powerful start and were ahead after just three minutes as a relentless driving maul was halted illegally by Tonga and referee Nic Berry awarded a penalty try.

But not only were Tonga seven points adrift, they also had Fifita sin-binned for trying to illegally stop the Wales forwards, and the home side prospered by claiming a second touchdown just three minutes later.

Tonga were again their own worst enemies, losing lineout ball on their own throw, and Wales did not require a second invitation to attack as Aaron Wainwright crashed through two tackles and flicked a scoring pass to Biggar, who also added the conversion.

Takulua opened Tonga's account through a long-range penalty, but Wales rapidly resumed normal service as they claimed a third try in nine minutes through more impressive work by Wainwright, before debutant full-back Jonah Holmes freed Williams.

The Saracens back still had plenty to do under pressure from Mafi, but he finished brilliantly in the corner, and Biggar's conversion opened up a 21-3 advantage.

Tonga briefly mounted an attacking phase, yet they were fortunate not to lose another player midway through the half when flanker Dan Faleafa took out Wainwright late and high.

Berry awarded only a penalty, that Biggar kicked, but match citing commissioner Peter Ferguson is likely to take a much closer look.

Tonga, though, did not lose heart, and another spell of pressure was rewarded when Fifita claimed a close-range touchdown that Takulua converted, which should have wiped out any hint of Welsh complacency.

But Tonga were on a roll, and they gave Wales even more to think about on the stroke of half-time after impressive work by Vailanu led to a touchdown for Mafi, with Takulua's conversion cutting the deficit to 24-17 at the break.

Wales had lost all their impressive early momentum, and they blundered again early in the second period when Tomos Williams' pass from an attacking Wales lineout was intercepted by Vailanu, who sprinted 60 metres for a superb try that Takulua converted.

But Tonga were only level for three minutes, with Biggar creating a try for Evans when his cross-kick into space was gathered at full speed by the Scarlets wing for a try which Biggar converted, making it 31-24.

Tonga had finally run out of steam, and Wales scored at regular intervals after that, amassing 50 points during the second period to set themselves up for next Saturday's clash against the Springboks.