Lewis Hamilton says he wants answers from Mercedes after engine failure cost him victory at the Malaysian Grand Prix and severely dented his title hopes.
The failure was the latest in a series for Hamilton, who is 23 points behind team-mate Nico Rosberg with five races to go and 125 points still available.
"We have so many engines for eight drivers and mine are the only ones failing," said the Briton.
"Someone has to give me some answers because it is just not acceptable."
Daniel Ricciardo beat Max Verstappen in a Red Bull one-two in a gripping race.
Hamilton said: "To be fighting for the championship and only my engines are failing just doesn't sit right with me.
"There have been many decisive races but this is definitely one of those. Something or someone doesn't want me to win this year but I won't give up. I will keep pushing."
Asked later to clarify what he meant by "someone", Hamilton said: "A higher power. It feels right now as if the man above or a higher power is intervening a little bit. But I feel I have been blessed with so many opportunities. So I have to be grateful for those. While this does not feel great, I have to remain grateful."
Mercedes F1 boss Toto Wolff said: "It's clear he is super-frustrated. He has been really unfortunate this year. He is losing many points but the championship is not over yet.
"I am so gutted for Lewis. He was in control of that race. Not good."
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Hamilton dropped 43 points behind Rosberg after the first four races, in large part because of two identical engine failures in qualifying in consecutive races in China and Russia that forced him to start down the grid.
Hamilton fought back with six wins in the next seven races to take a 19-point lead into the summer break.
Rosberg won in Belgium where Hamilton had to start from the back of the grid after taking new engines to replace the ones that had failed earlier in the year, and a bad start from pole position led to Hamilton finishing second to the German at the next race in Italy.
Rosberg dominated in Singapore, where an out-of-sorts Hamilton finished third, to take an eight-point lead. Hamilton looked set to retake the championship lead in Malaysia only for his engine to fail.
Hamilton has a chance to claw back some of his deficit next Sunday at the Japanese Grand Prix.
He said: "I'm just going to try to recollect myself and get myself together for the next race and try to perform as I did this weekend."