Arsenal's new Nigerian star Nwankwo Kanu walked straight into a cheating storm as he laid on the FA Cup holders' 76th-minute winner for Marc Overmars and sparked furious protests from Sheffield United in the fifth round FA Cup tie at Highbury.

United boss Steve Bruce appeared to want to take his team off the field following the goal and the game was held up for eight minutes while players from both sides jostled each other in an explosive confrontation.

The mayhem started when teenage United striker Lee Morris went down under challenge from Gilles Grimandi in the Gunners' penalty area.

United's appeal for a penalty were rejected and as Morris limped off injured, the ball ran out for an Arsenal throw-in.

Ray Parlour tried to throw the ball to United keeper Alan Kelly to give the visitors' unchallenged possession.

But Kanu, who had come on as a 65th-minute substitute and may have been unaware of the unwritten code of sportsmanship which is followed in this country in such circumstances, hunted the ball down and slid a low cross into the path of Overmars who tapped into an empty net.

United players could hardly believe their eyes but once they had recovered their senses they surrounded referee Peter Jones and a linesman with their protests.

Then an angry Bruce jumped out of the dug-out, signalling for his players to come off the field.

United fans, guarded by an army of security men, chanted "shame on Arsenal" for the rest of the game but the referee, once all the mayhem had died down, was left with no option but to let the goal stand.

Arsenal had appeared to be heading for a comfortable victory when Patrick Vieira headed them into a 28th minute lead from Denis Bergkamp's exquisitely curled free-kick. Diawara, who made a surprise starting debut in place of his French compatriot Nicolas Anelka, last Wednesday's two-goal Wembley hero for the world champions against England, twice hit a post within the space of three minutes towards the end of the first-half.

And Overmars was only inches off target with two other block-busting efforts as United's defenders fell apart against a patient and finally penetrating wave of Arsenal attacks.

But three minutes after the interval United's Brazilian striker Marcelo, who had terrorised Arsenal's defence - lacking the injured Tony Adams, Martin Keown and Lee Dixon, easily rose above Grimandi to nod home Paul Devlin's cross.

United, who knocked Arsenal out of the cup three years ago in a fourth-round replay having drawn at Highbury, clearly fancied their chances of repeating the trick at that stage and their heavily reinforced back line reduced the Gunners to frustration in the second half.

But when Kanu, the £3million signing from Inter Milan whose career was threatened three years ago when he needed heart surgery, made his entry it led to a frenzied finale.

He was unlucky not to score with a fierce shot that brought goalkeeper Kelly to his knees but then became the villain as far as Sheffield were concerned when he pounced on Parlour's throw in and re-routed it beyond the helpless Kelly for Overmars to tuck away.

In the scrimmage that followed, Overmars appeared to take a blow in the face from Ian Hamilton, one of five United players who were booked in the match and when the game finally got going again it was almost a sheepish Arsenal that held on desperately for their dubious victory.

Teams:

Arsenal: Seaman, Vivas, Bould, Grimandi, Winterburn, Parlour, Garde (Hughes 43), Vieira, Overmars, Bergkamp, Diawara (Kanu 64).

Subs Not Used: Anelka, Manninger, Upson.

Goals: Vieira 28, Overmars 76.

Sheff Utd: Kelly, Derry, Sandford, Holdsworth, Quinn, Morris, Woodhouse, Hamilton, Stuart, Devlin (Twiss 83), Marcelo.

Subs Not Used: Ford, Tracey, O'Connor, Jacobsen.

Booked: Stuart, Hamilton, Holdsworth, Derry, Marcelo.

Goals: Marcelo 48.

Att: 38,020

Ref: P Jones (Loughborough).