Reigning champion Francesco Bagnaia has won the MotoGP Japanese Grand Prix sprint after leader Pedro Acosta crashed out with four laps to go.

The Italian rider's victory on Saturday moved him to within 15 points of championship leader Jorge Martin, who finished fourth.

Rookie Acosta, who took pole earlier in the day, had overtaken Bagnaia on the third lap to take the lead, but lost control near turn seven, losing the opportunity to win his first MotoGP sprint.

Bagnaia, who moved to 357 points ahead of Sunday's race, fought off second-placed Ducati teammate Enea Bastianini by 0.181 seconds amid occasional rains in Motegi.

"We had to sacrifice a bit of performance during the race to understand the conditions better. I'm very happy because with this condition it's not very easy to win," Bagnaia said in his post-sprint interview.

Pramac Racing's Martin, who started from 11th on the grid after crashing during qualifying, began well to take fifth position in the first lap, facing pressure from Marc Marquez, who eventually overtook him.

Marquez momentarily took second place from Bastianini, but he recovered to leave Marquez third.

"Nice sprint, the pace was very good. I lost time in the last two or three laps," Bastianini, third in the championship, said after the race.

LCR Honda's Takaaki Nakagami crashed out of his home grand prix sprint after a collision with teammate Johann Zarco, while Red Bull KTM's Brad Binder, sixth in the championship, quit due to an issue with his bike.

"We're investigating what happened to cause Brad Binder's sprint to come to a premature end," the team wrote on social media platform X.

"For now, all we can do is apologise to Brad."