A homemade bomb carried by a woman killed three people and injured at least 21 in an explosion near a restaurant in central Moscow on Saturday evening, authorities said.

The explosion occurred just before 8pm close to an Italian restaurant located in one of Moscow’s seven Stalin-era skyscrapers at Kudrinskaya Square, the police said.

Russia’s anti-terrorism committee said an unidentified woman had tried to get into the restaurant but was stopped by a security guard, the state RIA news agency reported.

It said the woman, the security guard and a customer at the Balzi Rossi Italian restaurant were killed in the blast that followed.

Those injured received wounds of varying seriousness, the police said. Russia’s state RIA news agency released video of heavily armed law enforcement officers at the scene, which had been closed off to the public.

The authorities did not name those killed or injured nor did they say who they thought might have been responsible.

The Kommersant daily newspaper cited its own sources as saying that the bomb had been intended to maim and kill guests on the restaurant’s summer terrace outside.

It suggested the bomb had been set off by someone else remotely and that the woman carrying it may not have known it was a bomb.

The restaurant’s website said the venue had been closed on Saturday for a private event.