The 23-year-old midfielder only joined the Portuguese outfit from Standard Liege last summer in a £6.5million deal, signing a five-year contract at the Estadio da Luz.
As Manchester United look to bolster their midfield department in the summer, the reigning Premier League champions will need to move quickly in order to bring him to Old Trafford, after reports by French newspaper Le Parisien claimed PSG had already made contact with the player's representatives.
Witsel played a major role in helping Benfica produce an impressive Champions League comeback over Zenit St Petersburg last week, and is thought to have attracted interest from a host of top European clubs.
Manchester City and Chelsea are also believed to be monitoring the situation, and could spark a four-way bidding war for one of the Portuguese Primera Liga's most sought-after stars.
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