A human rights group, Section27, on Wednesday called on the South African government to denounce the conviction of a gay couple in Malawi.
It wants the South African government to raise the matter with the Southern African Development Community (SADC).
"We believe that the Malawian government needs to protect its citizen's rights," said Section27 executive director Mark Heywood in a statement.
The organisation would hold an "emergency picket" outside the Malawian High Commission in Pretoria at 11am.
This followed the conviction in a Malawian court on Tuesday of gay couple, Steven Monjeza and Tiwonge Chimbalanga, for committing "unnatural acts".
They were arrested in December 2009 after celebrating their engagement.
Heywood said that continued action against gay, lesbian, bisexual and transgender people in Zimbabwe, Malawi and Uganda was a gross violation of human rights.
"In allowing this abuse to continue, the door has been opened to reversing and retard progress on all human rights, including the right to dignity and full social, legal and political equality for women and freedom of expression and the media amongst others," Heywood said.
The picket was aimed at drawing the world's attention to the matter.
The pair was due for sentencing on Thursday. They could face up to 14 years in jail.
"We hope that the Malawian ambassador and his government will hear our voices and know that much louder protests will be heard across the world in days to come."
Section27, which incorporates the Aids Law Project, is a South African-based public interest law centre.
According to its website, it seeks to influence, develop and use the law to protect, promote and advance human rights.
It is named after section 27 of the Constitution, which covers rights relating to health.