A lobby group on Monday asked a South African court to reinstate an advertisement urging President Jacob Zuma to act against the trade in lion bones, which was removed from the country's main airport.

The advert pictured Zuma in the background of a poster of a lioness looking down the barrel of a gun with the text "President Zuma can save her life".

The posters were removed from Johannesburg's OR Tambo International airport last August just nine days into campaign group Avaaz's month-long contract. Avaaz claims this act violated its right to freedom of expression.

"The government violated that right (to freedom of expression) when they tore down that advert... calling on President Zuma to act to save stop lions from the lion bones trade," Emma Ruby-Sachs, Avaaz campaign director told AFP.

"The government got scared and in a secret email they revealed that they feared the advert becoming a public relations nightmare for the president," she said.

Local media quoted the email from a top airport official as saying there was "an implicit message" in the advert that Zuma "is standing by while our lions are being killed and is thus complicit in the killings."

The global campaign group in June last year launched an online petition to get the government to act against the trade in lion bones -- a hot commodity for their use in Asian medicine and to make "bogus sex potions", the group says.

Some 750,000 people have signed the petition.

"If we can show President Zuma that this brutal trade is hurting South Africa's image as a tourist destination, he could ban and punish the trade in lion bones," reads the petition.

Avaaz said South Africa is the largest exporter of lion bones and that the latest government statistics show a 250 percent hike in such exports between 2009 and 2010.

Most of the bones come from animals legally hunted at South Africa's lion breeding farms.

Conservationists fear that a rise in demand may encourage poaching and threaten lions in the wild. Only about 20,000 wild lions remain on the continent.