Dual MotoGP champion Francesco Bagnaia has won the Japanese Grand Prix to complete a weekend double and cut his gap to rival Jorge Martin at the top of the world championship to 10 points.

The Ducati rider, who qualified in second after dominating practice and won Saturday's sprint, kept Martin at bay for 20 laps to clinch an eighth win of the season for the first time in his career.

Martin's second place at Motegi on Sunday moved him to 392 points while Bagnaia is second on 382, with four races left in the season. Marc Marquez took third.

"I feel super happy. We managed to gain 11 points during this weekend," said Bagnaia, whose win was the 900th by an Italian in MotoGP history.

The race began in overcast conditions at Motegi's Twin Ring circuit, with pole-sitter Pedro Acosta overtaken before the first turn of the first lap as Bagnaia darted past him into the lead.

Championship leader Martin (Pramac Racing) began in the fourth row after crashing during qualifying, but had a spectacular opening lap as he launched himself off the line and quickly moved from 11th to fourth.

The battle for the riders' championship came to the forefront in the fourth lap when Martin rose to second as he overtook Brad Binder and rookie Acosta, who crashed in Saturday's sprint, went down again.

Bagnaia managed the race well and kept a healthy distance between himself and Martin.

"Jorge today was much stronger, so I was just trying to manage the gap," Bagnaia added.

"I think the pace was incredible. We have to move on to the next one with the same ambition, the same strategy, and try to continue like this."

Alarm bells went off for Ducati in the 22nd lap as the Spaniard cut down the lead to 0.8 seconds with a blistering run.

It was too little too late however, as Bagnaia was warned of the danger and upped his pace to shut down Martin's challenge.