A homemade bomb carried by a woman killed three people and injured at least 21 in an explosion near an upscale restaurant in central Moscow on Saturday evening, the authorities said.
The explosion occurred just before 2000 local time close to an Italian restaurant located in one of Moscow's seven Stalin-era skyscrapers at Kudrinkskaya Square, the police said.
Russia's Anti-Terrorism Committee said that 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 had been 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.
More than four years into a full-scale war with Ukraine, Russia's FSB security service said earlier this year that authorities would step up protection for high-ranking military officials after a series of assassinations and attempted killings it blamed on Kyiv.
The Kommersant daily newspaper cited its own sources as saying that the bomb had been intended to maim and kill guests who were enjoying themselves on the restaurant's summer terrace outside.
It suggested that the bomb had been set off by someone else remotely and that the woman carrying it may not have known that it was an explosive device.
The restaurant's website said the venue had been closed on Saturday for a private event.

Trump says US, Israel to hold off on fresh Iran attack in hope of quick deal
Israeli strikes kill two in Gaza, destroy medicine storage warehouses
Thirteen die in tourist plane crash over Peru's Nazca Lines
All 10 climbers confirmed killed in Pakistan avalanche
Russia pounds Kyiv with missiles, killing at least ten
Trump says deal reached to disarm Hamas, Israeli support for plan remains uncertain
Kuwait intercepts new wave of Iranian attacks
Wildfires spread across Greece, conditions worsen in France and Spain
