Arsenal [Images] clinched top spot in Champions League Group B and maintained their 100 percent record in this season's competition as a late Robert Pires penalty secured a 1-0 win over 10-man FC Thun on Tuesday.

The result leaves the London [Images] side five points clear of Ajax Amsterdam, who beat Sparta Prague 2-1 in the other group game, with unlucky Thun stuck on three points and facing a battle with the Czech side, who have just one point, for a UEFA [Images] Cup slot.

Arsenal manager Arsene Wenger was relieved to see his side, who were playing without several first team players through injury, escape with a victory since they were second best for much of the match against a stubborn Swiss team.

The English side's task was made easier when their unfancied opponents had Cameroonian defender Armand Deumi sent off after just 35 minutes for a professional foul on Robin Van Persie.

Incredibly, though, Thun dominated the second half and had two 'goals' disallowed for offside leaving Arsenal seemingly headed for an embarrassing goalless draw until they were awarded a controversial penalty in the 88th minute.

Referee Lucilio Batista had originally waved away the appeals that followed Selver Hodzic's tackle on Van Persie but the assistant referee convinced him it was a foul -- allowing substitute Pires to slot home the winner.

SYMPATHETIC WENGER

"I am sympathetic for Thun and I was really sorry when their player was sent off," Wenger said. "The level of the game dropped after that and we also lost our concentration. But the referee had no choice."

Having already made sure of their progression from the group stage, Arsenal made six changes to the side that started Saturday's 3-2 Premier League win at Wigan Athletic.

With regular strike partners Van Persie and Thierry Henry [Images] in action from the start, though, the accomplished visitors were still strong favourites to overwhelm the tiny Swiss team.

Things began brightly enough for Arsenal with a powerful Van Persie strike narrowly turned away by Thun goalkeeper Eldin Jakupovic in the 20th minute.

Surprisingly, it was the home side who took charge after Deumi's sending off with Thun even finding the net twice in the second half only for both efforts to be ruled out for offside.

The second decision seemed particularly harsh with Swiss international Mauro Lustrinelli appearing comfortably onside as he glanced home a Nelson Ferreira free kick in the 66th minute.

"We had a legitimate goal disallowed and then conceded a penalty that the referee didn't give only to then let himself be convinced by his assistant," complained Thun manager Urs Schoenenberger.

THIRD SPOT

"But we can't allow ourselves to lose concentration now as we have to focus on securing third place in the group to earn a place in the UEFA Cup."

Thun, who were also unlucky to lose 2-1 at Highbury to an injury-time Dennis Bergkamp goal in September, can clinch a UEFA Cup spot with a draw at bottom side Sparta Prague next month.

Arsenal have no such worries, having won all five of their Champions League matches this season -- and a club record six including their final game last term -- making their final meeting at home to second-placed Ajax effectively meaningless.

"It was important for us to finish the job and finish top of the group," Wenger said, "because it guarantees that we play our second game in the knockout stage at home and get to play one of the second-place finishers from another group.

"It gives us confidence too but we're not going overboard. The real competition starts now and we know it will be a different type of competition because of it being a knockout."

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