CAPE TOWN, South Africa (Reuters) -- At least 20 people were injured on Tuesday when an explosion ripped through the Planet Hollywood restaurant in Cape Town's popular waterfront, witnesses said.

"At the moment it seems like it was a bomb. I heard the bomb explode and I came running," said a police officer who was among the first people on the scene.

The explosion occurred in the U.S.-franchised restaurant around 7:30 p.m., while it was packed with tourists and after-work revelers.

"It seems like something was thrown into the restaurant from outside," the policewoman said.

A Reuters correspondent on the scene said she saw at least 20 people being carried from the restaurant, many of them covered in blood. A waitress said she saw a woman whose legs appeared to have been blown off.

Cape Town, South Africa's foremost tourist venue, has been the scene of an escalating war between gangs who run the city's drug business and Muslim activists calling themselves People Against Gangsterism and Drugs.