Derek Adams' side remain stuck in the relegation zone as four second-half goals see the Highland outfit fall to defeat on their first league visit to Celtic ParkScott Brown and James Forrest as well as a double by Gary Hooper saw Celtic comfortably ease past relegation candidates Ross County.
The win sees the Scottish Premier League leaders extend their lead at the top of the table to five points after Motherwell’s defeat to St Mirren on Friday evening.
Neil Lennon made two changes from the side that defeated St Mirren last week, with Emilio Izaguirre and Lassad Niouoi coming in for Adam Matthews and Mikael Lustig.
Ross County brought in Mihael Kovacevic and Rocco Quinn for Ross Tokely and Mark Fotheringham, who started during the draw to fellow relegation strugglers Dundee last Saturday.
Celtic had two good chances to take an early lead, as firstly Lassad had a header from an Izaguirre cross from the left before Charlie Mulgrew had a strike at goal after a Georgios Samaras free kick, but on both occasions Mark Brown saved well to prevent his former side from going ahead.
Lennon’s side completed a superb move which started from the back and then finished off with Lassad mishitting an Izaguirre cross. The rebound fell to Hooper, but the striker’s effort was blocked for a corner.
The ball then went up the other end as a lapse in the Celtic defence saw Alex Cooper claim possession and play in Quinn on the edge of the area, but his strike was poor and allowed Forster to get down to save easily.
Just before the break Forster was called into action again to keep the score level as Quinn put in Cooper on the left-hand side, but the former Liverpool youngster’s strike was straight at the English shot-stopper.
Within a minute of the second half starting Celtic took the lead when Hooper played in Brown on the right of the penalty area and the Hoops skipper marched forward, before playing the ball into the corner of the Staggies' net.
Celtic got their second goal only a few minutes later as Victor Wanyama strode forward, finding Lassad on the left wing, and his inswinging cross was met by the head of Hooper, who diverted the ball beyond the helpless Brown.
The three points were wrapped up for the home side as a corner from the right by Mulgrew was headed into the danger area by Wanyama, who got above Staggies goalkeeper Brown and allowed Hooper to head home from close range.
Hoops boss Lennon was handed a boost as substitute Forrest received the ball on the right wing, cutting into the box and past the Ross County defence, before placing the ball beyond Brown for the fourth of the game.
Hooper should have sealed his hat-trick late on as Forrest found fellow substitute John Heron and his strike at goal was deflected towards goal by the English striker, but it smacked off the bar and away from danger, with the home side having to settle for a four-goal victory.