South Africa have been penalised five runs for ball tampering against Pakistan during the third day of the second cricket Test.

Umpires Ian Gould and Rod Tucker sanctioned the Proteas after tea on Friday when they found a change in the condition of the ball.

Television replays showed Faf du Plessis was rubbing the ball over a zip on his thigh.

The umpires summoned South Africa captain Graeme Smith, changed the ball, and Gould signalled five penalty runs.

Pakistan were 3-67 at the time, trying to score 418 to avoid an innings defeat.

South Africa made a mammoth 517 in their first innings and removed both Pakistan openers, Shan Masood and Khurram Manzoor, without scoring before lunch to further close in on a series-levelling win at Dubai stadium.