Yael Farber's 90-minute adaptation of August Strindberg's Miss Julie, set in the Karoo, is nothing but mesmeric and relentless as it looks at the effects of apartheid on modern South Africa.

But the audience giggled incessantly, and sometimes broke into raucous laughter at the most inopportune moments and during poignant dialogue on stage.

This left the cast, and indeed Farber, bemused. The Canadian-based director had come home to see the show at the start of its month-long run in Pretoria.

"Yes, South Africans are very different," Farber said backstage.

"When we had the show internationally, and especially in Scotland [as part of the Edinburgh Fringe Festival] there was literally one scene only during which the audience laughs, and for the rest of the time you could hear a pin drop.

"The only time you would hear noise again was at the end, when we got standing ovations.

"Tonight, the audience seemed almost jovial - I don't know whether that was embarrassment or what," Farber said.

Strong language and intense scenes of a sexual nature (and even a bit of nudity) in the play seemed to make the audience squirm in their seats.

Veteran Thoko Ntshinga, who brilliantly portrays the mother, Christine, said: "Scotland was different. It was dead quiet at all times and the audience sat on the edge of their seats. You knew you'd hit them by the ovation at the end."

On the laughter from the local audience, she said: "It depends where it hits. People don't just laugh - I think it might have been from embarrassment. In Scotland, you knew if there were South Africans in the crowd from the exclamations of 'yoh' and 'hayibo'."

Bongile Mantsai - who plays the servant John, who has an affair with farmer's daughter Julie - joked that he had received rave reviews for his toned buttocks and physique.

But he was serious when it came to Friday night's show: "The audience was a bit disturbing tonight, but you can't expect it to always be the same. It throws one off at times.

"There were certain parts where I, as a black man, while reading the script, felt pissed off.

"But if our younger generation reacted the way the audience reacted today it means there is a lot that we need to do.

"If we laugh at a mother for saying she lost her fingerprints from scrubbing the kitchen floor and raising other people's children, then it is a bit disturbing."

Mantsai and Hilda Cronje, who plays Julie, follow in the footsteps of Sandra Prinsloo and John Kani, who caused controversy by kissing on stage when Miss Julie was staged in Cape Town more than 25 years ago.

Judging by the responses from the audience on Friday night, interracial relationships and apartheid still provoke strong and uncomfortable reactions.