The result equalled Barca's worst in Europe, last achieved by Bayern Munich at the semifinal stage fours years ago, but could easily have been worse as they were outfought, outrun and outclassed.

Former Real Madrid playmaker Di Maria opened the scoring with a fine free kick on his 29th birthday and curled home a second in between efforts from Draxler and another birthday boy, 30-year-old Cavani.

Barca were flat from the off, with the likes of Luis Suarez, Lionel Messi, Sergio Busquets, Andres Iniesta and Gerard Pique reduced to bystanders by a lean, focused PSG display.

When the sides reconvene for the second leg at Camp Nou, even their very best may not now be good enough to save the tie.

Unai Emery was without the suspended Thiago Motta and the injured Thiago Silva but saw huge performances in their absence, with Champions League debutant Presnel Kimpembe, Marco Veratti and Adrien Rabiot all rivalling the goal scorers.

The home side took control of proceedings quickly, dictating the tempo and probing at the edges of the Barcelona defence.

Sergi Roberto needed to be alert to block Cavani's shot after Di Maria's incisive ball over the top and Marc-Andre ter Stegen was twice required in the first 10 minutes.

He responded well on both occasions, racing from his box to dink the ball over the pursuing Blaise Matuidi then saving well from the France midfielder after good work from Rabiot.

The pressure told in the 17th minute after Draxler coaxed a foul from Samuel Umtiti just a couple of yards outside the box. Di Maria struck the ball beautifully, getting his effort up and down in time to leave Ter Stegen no chance.

It took Barca time to respond but when they did, thanks to Neymar's powerful run and pass, it was nearly 1-1.

With Neymar drawing defenders towards him Andre Gomes found room on the overlap, collecting a measured pass only to see goalkeeper Kevin Trapp divert his shot wide.

A Barca break, predictably orchestrated by Neymar, left them exposed on the counter and PSG came close to a second in the 33rd minute when Draxler breezed past Roberto and struck at the near post. Ter Stegen, flinging a glove to his right, made the save.

They deservedly doubled their advantage before half-time after an off-colour Messi gave up possession to Rabiot in midfield. Veratti advanced at speed and when he switched the play to Draxler 12 yards out, the German buried his shot.

The second half was even more one-sided, with La Liga's reigning champions lethargic and susceptible to PSG's pace and purpose in attack.

It took them just under 10 minutes to score again, this time building from the back and sweeping aside a tired press from the Barca frontline.

Di Maria was the ultimate target and he was inexplicably allowed to cut in from the right, unchallenged as he moved into shooting range and bent a left-footed effort into the corner.

The tracking may have been lacking, notably from Iniesta, but Di Maria's execution was superb. Moments later he was gone, replaced by Lucas Moura after a memorable hour's work.

The fourth felt inevitable and was threatened on several occasions before Thomas Meunier sauntered upfield and slotted in Cavani. With Pique failing to get tight enough, the striker calmly dispatched his shot past Ter Stegen.

Umtiti somehow headed against the post from a yard as the lifeline of an away goal evaporated but Luis Enrique's humbled outfit might easily have walked away with an even more damaging defeat.