A powerful explosion in the heart of Moscow, a stone's throw from the Kremlin, killed eight people and injured dozens last night.
It raised the spectre of a repeat of the bomb havoc that left some 300 people dead in the Russian capital around this time last year and sparked the Chechen war.
The blast occurred in the middle of the evening rush-hour at one of the most congested points in the city centre, at an underpass by the Pushkin monument on Tverskaya street, Moscow's Oxford street, which leads directly to the Russian parliament, Red Square and the Kremlin.
Senior government officials promptly described the explosion as a terrorist bombing and the finger of suspicion was pointed at Chechen separatist rebels engaged in their second war with Russia in the past five years.
Acrid black smoke was still billowing from the underpass hours after the blast as bloodied victims lay around on the pavements being bandaged and treated for injuries by teams of medical workers. The injured, put at 53 by the Moscow emergencies department, included three children and a pregnant woman.
Several hours after the blast, at least seven dead were still buried in the rubble of the underpass, according to Moscow police. The death toll was expected to rise as 11 of the injured were in critical condition. The underpass connects three metro stations and is an extremely busy crossing point lined with kiosks.
The President, Mr Putin, immediately summoned an emergency meeting of his security chiefs, suggesting that the Kremlin took the view that the explosion - at first thought to be possibly accidental - was a deliberate attack. It was then announced that Mr Putin would personally oversee the investigation.
The mayor of Moscow, Mr Yuri Luzhkov, immediately visited the scene, cordoned off by hundreds of police, medical workers, and the security services. "The nature of the crime is obvious," he said. "The explosion hit in a place packed with people at rush hour."
One of his aides, Mr Alexander Muzykantsky, said that "exhaustive measures need to be taken" to foil a repeat of last year's bombing campaign.
People fled in panic from the teeming underpass when the blast erupted just before six in the evening, many of them pouring blood and covered in grime.
"The most terrible thing was this woman running out screaming for her son, her son," said one middle-aged man who emerged from the underpass unscathed.
Another woman working in one of the dozens of little kiosks that line the underpass was struck by debris from the blast. "I was sitting reading a book, then the lights went out. The door I was supposed to go through was jammed. It was pitch dark. I climbed through a window," she said. "I thought if I don't get out now I'll die."
Explosives experts from the FSB, the successor to the KGB, donned protective clothing and went into the underpass to try to pinpoint the source of the explosion. Officials said another bomb was found and defused.