South Africa fast bowler Andre Nel was fined half his match fees for sticking out his tongue to a West Indies player on the final day of the first cricket Test in Johannesburg on Tuesday.

Acting on a complaint by third umpire Brian Jerling, match referee Ranjan Madugalle conducted a disciplinary hearing and charged Nel under a section of the ICC Code of Conduct, which bars players from making an obscene gesture.

Nel was hit for two successive fours by Chris Gayle, who came to bat down the order as he was injured on the first day of the Test while fielding. But off the next ball, Nel had Gayle caught behind by wicket-keeper Mark Boucher.

Nel ran down the track with his arms in the air to celebrate the dismissal and as he passed by a dejected Gayle, stuck out his tongue to tease the batsman.

Gayle, who made 26, did not appear pleased at all.

The unsporting behaviour by Nel soured South Africa's convincing 189-run victory which gave them a 1-0 lead in the five-Test series.

South Africa skipper Graeme Smith said Nel tends to get aggressive when he bowls.

"He is such a placid bloke but when he gets that red cherry in his hand he changes," Smith said.