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Marshawn Lynch did NOT want to sign autographs for fans at LAX on Monday -- and he smacked a cell phone out of a fan's hand and spit in his direction to make his point.

Lynch had just touched down at LAX when he was approached by two guys -- a 17-year-old and an 18-year-old.

The guys tell us they knew someone on Marshawn's flight who tipped them off so they decided to head to LAX to try and get an autograph.

At first, Marshawn approached the 18-year-old and slapped the phone out of his hand. Lynch then went inside the terminal and came out a few minutes later and spit in their direction as he walked past them.

The owner of the phone says it got cracked in the incident and he's considering filing a police report for assault.

We reached out to Lynch's camp for comment. So far, no word back.