Paris Saint-Germain slumped to a dismal 2-0 defeat against Rennes in Ligue 1, with Karl Toko Ekambi and Arnaud Kalimuendo netting to amplify the pressure on Christophe Galtier.

PSG were booed off at half-time by the Parc des Princes crowd after Toko Ekambi broke in behind to hand Rennes a surprise lead, following a series of misses from Kylian Mbappe.

Things quickly went from bad to worse for the disjointed leaders, with former PSG forward Kalimuendo converting Lesley Ugochukwu's cross to provoke more fury from the home fans.

PSG's four-game winning run in Ligue 1 ended with a whimper as Rennes stood firm, and Galtier's under-fire side could see their lead at the summit reduced to seven points when Marseille visit Reims later on Sunday.

Mbappe endured a miserable first half for PSG, seeing a one-on-one finish disallowed for offside 22 minutes in before squandering three good opportunities.

Having drilled one left-footed effort narrowly wide, Mbappe was twice released in behind by measured throughballs from Lionel Messi, only for Steve Mandanda to deny him with firm saves.

Mbappe's misses were punished on the stroke of half-time as Rennes scored against the run of play — Toko Ekambi latching onto a simple ball over the top to fire into the bottom-left corner. 

PSG found themselves 2-0 down within three minutes of the restart, Kalimuendo side-footing home after Marco Verratti's giveaway allowed Ugochukwu to break down the left.

Toko Ekambi and Kalimuendo almost claimed braces as Rennes continued to press — the latter denied by a one-on-one save from Gianluigi Donnarumma.

Verratti forced a flying save from Mandanda late on, but that was as close as PSG went.

What does it mean? Bogey team pile pressure on PSG

While PSG attracted plenty of criticism for their meek Champions League elimination at the hands of Bayern Munich earlier this month, a run of four successive league wins had seen the Parisians ward off any potential threat to their domestic crown.

That run, however, came crashing to a halt against PSG's bogey team on Sunday. Rennes have now won four of the teams' last seven league meetings (D1 L2) — including a 1-0 victory in January's reverse fixture.

PSG have only lost two games without scoring in Ligue 1 all campaign, with both of them coming against Rennes.

Mbappe misfires 

Mbappe approached the game looking to become PSG's outright leading goalscorer in Ligue 1 history, having matched Edinson Cavani's total of 138 league goals for the club against Brest last week.

However, the France star endured a rare off-day, failing to hit the net despite leading all players on the pitch for shots (six), shots on target (three) and expected goals (1.0).

Genesio on top 

Rennes boss Bruno Genesio is the coach with the most league wins against PSG since the club's 2011 takeover by Qatar Sports Investments (six), with Galtier second on four.

Of the bosses to face PSG at least five times over that period in Ligue 1, Genesio has the best winning percentage (50 per cent — 6/12).

What's next?

PSG host Lyon in their next Ligue 1 fixture after the international break on April 2, while Rennes take on high-flying Lens one day earlier.