Celtic needed a late strike from Kris Commons to secure a 1-0 home win over Elfsborg in the first leg of their Champions League third qualifying round match on Wednesday.
Anthony Stokes missed an early chance for the Hoops before James Forrest saw his effort hit the crossbar.
However, Elfsborg, who named on-loan Celtic striker Mohamed Bangura in their starting line-up, had opportunities of their own and Hoops keeper Fraser Forster did well to stop a fierce strike from veteran Anders Svensson.
Things turned ugly in a fiercely-contested second half in Glasgow with a spate of bookings for both sides.
Celtic had a penalty appeal turned down and a Scott Brown strike blocked before Commons headed Celtic into the lead in the 76th minute.
It means the Scottish champions will only take a slender advantage to the Boras Arena, where Elfsborg haven't been beaten since September 2011.
Celtic had named an unchanged line-up to the one that saw off Cliftonville last week as they looked to make home advantage count.
They nearly got off to the perfect start when Samaras nodded on a ball for Stokes who hooked his shot wide after just 15 seconds.
Stefan Ishizaki fired well over from distance moments later as Elfsborg immediately responded.
Before the match the headlines had all been about Bangura and the on-loan striker's every touch was accompanied by a chorus of jeers from the home fans.
The Sierra Leone forward had failed to score for Celtic in 16 appearances but soon tested Forster with a low drive from 25 yards that the keeper got down well to stop.
Celtic came close to breaking the deadlock after 20 minutes when Commons' cross from the left was met by James Forrest at the far post and his first-time effort clipped the top of the bar.
The Hoops had the ball in the net eight minutes later when Stokes fired past Kevin Stuhr-Ellegaard but the striker was judged to be offside when he collected Forrest's pass in the box.
Elfsborg's combative and pressing style gave Celtic very little time to settle in possession and they came close to a valuable away goal when Svensson's fierce strike from 20 yards was tipped onto the bar by the outstretched Forster.
Efe Ambrose then headed a Commons corner over under no pressure before Stokes saw his free-kick from the edge of the box tipped over right on half-time.
Celtic started the second half in determined fashion and when Stokes picked out Samaras in the box with less than a minute gone it looked like the opener was coming but the Greek striker's weak effort was stopped by the 'keeper's legs.
Both sides upped the tempo and some hefty challenges led to a spate of bookings for both sides. Stefan Ishizaki was first to go in the referee's book before Johan Larsson was fortunate to avoid being shown red for a cynical challenge on Samaras while Emilio Izaguirre was booked for a foul on Bangura.
A Celtic penalty appeal was waved away before Stokes then teed up captain Brown but his stinging strike for 25 yards was deflected out for a corner.
Time looked to be running out for the Hoops but Commons made the breakthrough when he stooped to connect with Izaguirre's cross and send a downward header past Stuhr-Ellegaard from close range.