Sam Darnold and the undefeated Minnesota Vikings continued their impressive start to the NFL season on Sunday with a 31-29 victory over NFC North rivals the Green Bay Packers.

Darnold, the revelation of the season so far, threw three touchdowns at Lambeau Field as Minnesota moved to 4-0 on the season – their best start in eight years.

Meanwhile, Super Bowl champions Kansas City ground out their fourth straight win, a 17-10 victory at the Los Angeles Chargers.

But the Pittsburgh Steelers suffered their first defeat of the season with a 27-24 loss to the Indianapolis Colts and their 39-year-old stand-in quarterback Joe Flacco.

The Vikings broke out to an early 14-0 lead thanks to Darnold finding Jordan Addison with a 29-yeard touchdown pass and then connecting with Josh Oliver on a pass at the end of the first quarter.

Minnesota continued to dominate in the second quarter, with Addison rushing in from seven yards and then Darnold finding his favourite target Justin Jefferson with a 14-yard pass to make it 28-0.

But the Packers gave themselves a lifeline at the end of the half when Jayden Reed collected a 15-yard pass from Love to reduce the deficit.

The Packers came roaring back in the fourth quarter with Love throwing touchdowns to Dontayvion Wicks and Tucker Kraft to cut the lead to six points.

A 33-yard Will Reichard field goal for the Vikings made it a two-score lead, however, and although Love found Wicks for another touchdown the attempted onside kick was taken care of by the Vikings and they held on for the win.

"We believe in each other more than anyone else believes in us, we have a really good formula but we need to learn and grow," said Darnold, reflecting on how they had let Green Bay back into the game in the second half.

Packers quarterback Jordan Love threw four touchdowns, but he was also intercepted three times as the Packers fell to 2-2.

The Chiefs made a slow start in Los Angeles and trailed 10-0 until four minutes left in the half – when star quarterback Patrick Mahomes threw a monster pass to Xavier Worthy in the end zone.

A Harrison Butker field goal tied the game in the third and the Chiefs secured the win with Samaje Perine rush up the middle. (AFP)