Lopez set up Lazio's opener

Porto were joined in the last four by Celtic, Lazio and Boavista.

The Portuguese side went into the game trailing 1-0 from the first leg, but Silva cancelled out that deficit within 16 minutes.

Helder Postiga created space for him to score his first goal of the night as he fired a shot inside the near post.

Porto dominated the midfield against a home side badly missing injured captain Angelos Basinas.

Panathinaikos improved as the game wore on with Nikos Liberopoulos forcing a good save from Vitor Baia.

Porto were content to defend for much of the second half and they silenced the home crowd in the extra period as Silva broke away from Yourkas Seitaridis to slot home the winner.

Match report: Liverpool 0-2 Celtic

Celtic won an all-British affair against Liverpool at Anfield 2-0 to go through 3-1 on aggregate.

Meanwhile, Lazio ensured their progression to the last four with a 3-1 win on aggregate against Besiktas.

Italian midfielder Stefano Fiore and Argentine Lucas Castroman were the scorers as Lazio eased to a 2-1 win in Istanbul.

Argentine striker Claudio Lopez provided the killer pass for Fioreto to put Lazio ahead after just six minutes.

This was a historic night for Boavista. The players deserve all the praise we can give them Boavista coach Jaime Pacheco

Four minutes later fellow midfielder Castroman rose to head home Lazio's second and put the result virtually beyond doubt.

Fiore and Lopez both had further chances, while Lazio's defender Fernando Couto cleared off the line after Ahmet Dursun's shot beat keeper Angelo Peruzzi.

Besiktas kept pushing forward but the hard-working Ilhan Mansiz failed to show his customary finishing after the break.

The Turkish side struck late through a Sergen Yalcin 83rd-minute strike, but Mircea Lucescu's men ultimately paid a high price for some slack defending early on.

Boavista completed the semi-final line-up by beating Malaga 4-1 on penalties.

The Portuguese side trailed 1-0 from the first leg and looked to be heading out of Europe until a late free-kick from Luiz Claudio levelled matters.

That goal was only the fourth Malaga had conceded in the Uefa Cup this season and sent the game into extra-time, where neither side were able to find the net.

Alexandre Goulart netted the fourth and decisive penalty for Boavista after successful strikes by Jorge Silva, Claudio and goalkeeper Ricardo Pereira, who also saved two spot-kicks.

It is the first time Boavista have made it through to the Uefa Cup semis and ends Malaga's 15-game unbeaten streak.