Martin O'Neill's men must conjure up the magic of Anfield again if they are to scale the heights of the Lisbon Lions in 1967 after being held to a controversial but action-packed draw in the UEFA Cup semi-final first leg.

Henrik Larsson gave Celtic hope with his 37th goal of the season a minute after Joos Valgaeren's own goal had undeservedly put the Portuguese side ahead.

But the Swede went from hero to villain by failing to score from the spot after the home side were eventually awarded a penalty after two appeals had been turned down.

That spoiled the biggest game for the club in 29 years having failed to reach this stage since being knocked out of the European Cup by Atletico Madrid in the 1974-75 season.

Celtic seemed to find the tag of favourites uncomfortable early on having sent Liverpool, Stuttgart, Celta Vigo and Blackburn tumbling en route to the last four.

But the home side almost carved out an opening in the seventh minute when John Hartson and Larsson combined well on the edge of the area.

Boavista goalkeeper Ricardo, however, was alert and quick off his line to prevent Stilian Petrov getting on the end of the Swede's clever throughball.

But Celtic were raging when they were denied a penalty in the ninth minute.

Didier Agathe breezed past Filipe Anunciacao in the box, but the Boavista man stuck out his arm to stop the ball from getting past him.

Frank de Bleeckere waved away protests and the referee rejected more loud claims from the home crowd moments later when Martelinho handled the ball following Larsson's flick.

Boavista, however, had a glorious chance to add insult to injury in the 18th minute when Pedrosa got away down the left and crossed to Luiz Claudio.

He directed the ball back into the path of Duda, whose shot deflected off Bobo Balde and spun wide from just eight yards out.

The Celtic crowd were again appealing for a penalty in the 43rd minute after accusing Eder of handling Agathe's cross, but de Bleeckere again looked disinterested.

Boavista coach Jaime Pacheco made a change at the break with Cafu coming on for Claudio and that brought a dangerous response from the visitors.

Johan Mjallby headed Pedrosa's corner straight to Duda on the edge of the box and he cut inside, but shot well wide of the mark.

Celtic failed to heed that warning and Boavista stunned the home crowd in the 48th minute by taking the lead in fortunate circumstances.

Martelinho fired in a hopeful cross from the right flank and Valgaeren left Rob Douglas flat-footed by slicing the ball into his own net.

The home side responded in the best possible fashion by hitting the equaliser less than a minute later.

Alan Thompson and Petrov combined to find Larsson in the area and he stabbed the ball past Ricardo from nine yards to send the supporters into ecstasy.

The yellow cards soon followed for Boavista as they looked to stand up to the inevitable barrage - with the Parkhead crowd again spurring their heroes on.

Neil Lennon had a nightmare in the 56th minute as Duda seized on his poor backpass. It was two against one as he played the ball infield to Duda - and Lennon bundled him over from behind to earn a booking.

From the resulting free-kick Douglas pulled off a fine save by his left post from Pedrosa's shot which somehow squeezed through the wall and then gathered.

Celtic were calling for another spot-kick moments later when Hartson looked to be fouled in the box by Avalos before Martelinho was booked for a foul on Petrov.

The match was alight now and Ricardo did well to hold on to Larsson's free-kick with a dive to his left.

The man with the mask Turra could not hide though moments later when he was booked for a reckless challenge on Larsson before Celtic turned the screw.

Hartson could have put the home side ahead in the 73rd minute when the ball somehow made its way through to him, but Ricardo saved from just four yards.

Celtic were finally awarded a penalty in the 75th minute after Eder had handled Thompson's deflected free-kick - but Ricardo guessed right and saved Larsson's effort by his right-hand post.

Thompson could not recreate his free-kick from Anfield and fired straight into the wall with seven minutes left.

Turra then thwarted a late Celtic goal by clearing Hartson's goalbound effort off the line to put Boavista in the driving seat for a trip to Seville.

But Liverpool will tell them that the result is far from a foregone conclusion.

Teams

Celtic Douglas, Mjallby, Balde, Valgaeren, Agathe (Sylla 74), Lambert, Lennon, Petrov (Fernandez 78), Thompson, Larsson, Hartson.

Subs Not Used: Marshall, McNamara, Maloney, Smith, Crainey.

Booked: Lennon, Balde.

Goals: Larsson 50.

Boavista Ricardo, Mario Loja, Paulo Turra, Avalos, Erivan, Eder, Anunciacao, Martelinho, Pedrosa (Rui Oscar 90), Duda, Luiz Claudio (Cafu 46), Cafu (Bosingwa 81).

Subs Not Used: William, Jorge Couto, Jocivalter, Yuri.

Booked: Duda, Avalos, Martelinho, Paulo Turra.

Goals: Valgaeren 49 og.

Att: 60,000

Ref: F De Bleeckere (Belgium).