France defender William Saliba put the Premier League leaders ahead with a towering header from a corner by Portuguese midfielder Fabio Vieira.

But Arsenal’s lead lasted just 12 minutes, Goncalo Inacionodding home the equaliser after hesitancy from keeper Matt Turner following a corner by English winger Marcus Edwards.

In an absorbing game in the Portuguese capital, Paulinho fired Sporting ahead only for Arsenal to equalise through an own goal by Japan midfielder Hidemasa Morita.

Both teams created numerous chances in a free-flowing encounter.

Former Tottenham player Edwards was denied by Turner when the score was 1-1 and Paulinho wasted a great chance to make it 3-1 to the hosts before a wicked deflection off Morita made it 2-2.

Arsenal had a chance to take a lead back to Emirates Stadium for the return leg next Thursday (20:00 GMT) but Vieira’s header was kept out by Antonio Adan.