Opener Dean Elgar struck his third Test century as South Africa rode their luck to finish the first day of the second Test against West Indies on 270 for two on Friday.

Elgar, who came into the match with his position under scrutiny, scored 121 as he shared a second-wicket partnership of 179 with Faf du Plessis which frustrated the touring side who were the architects of their own downfall as they let numerous chances slip in the field.

Du Plessis will resume on a patient 99 along with Proteas captain Hashim Amla, who scored a double-century in the first Test in Pretoria and has reached 17.

After being sent into bat, the day belonged to left-hander Elgar, who was involved in his fourth century stand in test cricket -- remarkably all with Du Plessis.

Following the early loss of out of form opener Alviro Petersen, caught at cover by Leon Johnson off Shannon Gabriel for 17, South Africa edged to 68 for one at lunch.

They pulled away in the afternoon session though as sloppy West Indies offered four lives to the batsmen and were made to pay for their profligacy.

SCORES IN BRIEF

SOUTH AFRICA: First innings 270 for 2 (Petersen 17, Elgar 121, Du Plessis 99 not out, Amla 17 not out; Peters 1-44, Gabriel 1-52)