Marseille's defeat against Nantes on Friday – their third in succession – presented Leonardo Jardim's side with the opportunity to bolster their position in the UEFA Champions League places, but Habib Habibou's late strike means their advantage is only two points.
Bernardo Silva had given Monaco the lead after 26 minutes with a clever finish at Stade Louis II on Saturday, but the hosts were unable to find a second goal and, after goalkeeper Danijel Subasic had been forced to make a couple of fine saves to preserve their advantage, Habibou salvaged a point for the visitors with three minutes left.
With Lyon playing Saint-Etienne on Sunday, Paris Saint-Germain took the chance to return to the top of the table with a 3-1 victory at Nice.
Once again, Javier Pastore showed his importance to Laurent Blanc's side with two goals either side of Mathieu Bodmer's first-half strike, the Argentine forward filling the void left by the suspension of PSG talisman Zlatan Ibrahimovic.
Edinson Cavani sealed the win six minutes after Pastore's second from the penalty spot, firing home after the Uruguay international had himself been fouled by Jordan Amavi.
At the bottom, there was a morale-boosting win for Metz against fellow relegation rivals Lens, Albert Cartier's side winning 3-1 to improve their survival hopes.
After Florent Malouda had scored an acrobatic opener, Ferjani Sassi missed a glorious chance for Metz with the goal at his mercy, but further strikes from Bouna Sarr and Modibo Maiga kept Metz's slim hopes of staying up alive.
Substitute Aristote Madiani scored his first Ligue 1 late on, but it was not enough for the Lens, who now look doomed to Ligue 2.
Toulouse – who saw Francois Moubandje sent off – leapt out of the bottom three with a 1-0 win over Lorient, who replace them in the danger zone.
Meanwhile, Reims' 2-1 win over Bastia sees them open up a three-point cushion to the relegation battle.
Evian remain in trouble after a 1-1 draw with Guingamp, who had Claudio Beauvue's 44th-minute opener cancelled out by Nicolas Blandi.
