Russian authorities said on August 2 that an improvised explosive device was detonated at a restaurant in central Moscow, killing three people and wounding 21 others, as investigators worked to determine who was behind the bombing.The National Anti-Terrorism Committee said the device exploded at a restaurant on Kudrinskaya Square, near the center of the Russian capital, around 8 p.m. local time on August 1.It said those killed were a woman suspected of bringing the explosive device to the restaurant, a security guard who stopped her from entering, and one of the restaurant's guests."An improvised explosive device was detonated in a restaurant," the committee said in a statement carried by Russian state news agencies.The 21 wounded suffered injuries of varying degrees of severity, according to the committee. It said operational and investigative measures were under way to establish the circumstances of the blast.The explosion occurred at about 8 p.m. local time on August 1 at the Balzi Rossi Italian restaurant, which is located in one of Moscow's Stalin-era skyscrapers.The restaurant had been closed for a private function, according to its website.Unidentified SuspectRussian state media reported that the explosive went off after the unidentified woman was stopped from entering the restaurant.Images released by Russian media showed heavily armed law-enforcement officers, ambulances, and emergency vehicles at the scene. Roads around Kudrinskaya Square were temporarily closed, while the area was cordoned off.Russian authorities have not identified the woman or the other victims. They have also not said who may have been responsible for the bombing or identified a possible motive.