Prime Minister Vladimir Putin on Tuesday declared that "retribution is inevitable" against those who masterminded an airport suicide bombing that killed 35 people, including at least seven foreigners.
But Putin and other officials kept an official silence about who might have organized the attack, even as unidentified law enforcement sources told Russian news agencies that suspicions were centering on a obscure rebel group called Nogai Battalion.
NTV television showed a photograph of the severed head of what it called the suspected suicide bomber, a man aged 30 to 35 and of North Caucasus or Arab appearance.
The Emergency Situations Ministry said 35 people died and more than 110 people remained hospitalized Tuesday after the attack in the public waiting area of Domodedovo Airport's international arrivals hall at 4:32 p.m. Monday. The Investigative Committee initially said the blast occurred in the baggage claim area.
Putin denounced the "abominable" attack after observing a moment of silence at a Cabinet meeting. "This was an abominable crime in both its senselessness and its cruelty," Putin said. "I do not doubt that this crime will be solved and that retribution is inevitable."
But the identity of the bomber remained a mystery amid conflicting information about whether the actual attacker was male or female or had accomplices.
A number of eyewitnesses recalled a man wearing a black jacket who had carried a bag and a suitcase that suddenly exploded.
The blast occurred after the man stepped into the lane between the customs exit and a crowd of people waiting to greet emerging passengers, eyewitness Artyom Zhilenkov told Gazeta.ru.
The theory of a bomb hidden in a bag or suitcase was supported by an Emergency Situations Ministry official, who told the online newspaper that this would attract less attention than an explosives belt worn under the clothes.
But several law enforcement sources later pointed to a female suicide bomber wearing an explosives belt and accompanied by a male companion.
"The explosion occurred at the moment the woman opened a bag. She was accompanied by a man whose head was blown off by the blast," one source told RIA-Novosti.
Investigative Committee spokesman Vladimir Markin said the explosives were probably attached to the bomber's body and not carried in a bag. Otherwise, he said, there would have been a crater in the floor.
The Investigative Committee said Tuesday that the bomb contained the equivalent of 5 kilograms of TNT and was fitted with metal accessories including bolts, wires and balls to inflict greater damage.
In recent weeks, investigators had been tracking three women and one man on suspicion that they might be preparing an attack on Moscow, Lifenews.ru reported, quoting law enforcement sources.
The report linked the airport attack to a mysterious blast that occurred on Dec. 31 on a shooting range in the city's southeast.
Media reports at the time said a massive explosion of some 7 kilograms of TNT that destroyed a vacation home on the range was accidentally triggered by terrorists preparing a bomb.
Eyewitnesses saw a woman fleeing the scene when the blast occurred, and rescuers found the remains of the widow of a slain North Caucasus rebel in the home, Rosbalt.ru reported.
On Jan. 5, police detained a 24-year-old medical student in the southern city of Volgograd on suspicion of handling explosives linked to the New Year's Eve blast.The student, Zeinap Suyunova, was reportedly married to a rebel arrested in a special forces operation last October.
Investigators are studying whether her husband and the husband of the woman killed in the Dec. 31 blast both belonged to the Nogai Battalion, a rebel group based in the Stavropol region, Rosbalt.ru reported.
The group has been linked to an unsolved explosion in Pyatigorsk last August that injured 30 people and an attempted bombing in Stavropol in September that was averted when residents alerted police about an abandoned car with explosives.
No one has claimed responsibility for Monday's attack, which has raised new concerns about safety at major sporting events planned over the next few years. Analysts said the bombers had probably singled out foreigners by targeting Domodedovo's international arrivals hall.
"In the face of the 2014 Sochi Olympics and the 2018 Football World Cup, authorities will face very tough questions about the security of foreign nationals here," said Andrei Soldatov, a security analyst with the Agentura think tank.
The International Olympic Committee was quick to play down such fears, saying Tuesday that it has "no doubt" that Moscow will deliver safe games in 2014.
FIFA president Sepp Blatter over the weekend formally awarded Russia the 2018 World Cup during a meeting with Putin in St. Petersburg. Prior to the signing, Blatter told Putin that he was certain FIFA had made the right choice.
Killed in the blast were British property consultant Gordan Cousland (Story, Page 3) and Ukrainian playwright Anna Mashutina, who wrote under the pen name Anna Yablonskaya and had arrived in Moscow to receive an award from the Cinema Arts magazine. Among the other foreigners were one from Austria, Germany, Kyrgyzstan, Tajikistan and Uzbekistan. Sixteen others were Russians, while the remaining 12 have not been identified.
At least nine foreigners were hospitalized, including Zuzana Fialova, a Slovak actress and member of the country's National Theater. Fialova, who wanted to visit performances in Moscow theaters, was in serious condition, Slovak media reported.
Four people were in extremely serious condition and 39 in serious condition, Health and Social Development Minister Tatyana Golikova said, Interfax reported.
The Foreign Ministry opened a consular office at Domodedovo to assist foreign relatives of those affected.
Meanwhile, President Dmitry Medvedev and Putin separately visited victims in hospitals.
During a visit to the Sklifosofsky Institute, Medvedev called the organizers of the bombing "bastards" whose "goal was to injure as many people as possible, Interfax reported.
Putin announced that City Hall and the federal government would jointly pay 3 million rubles ($101,000) to the family of each killed victim, 1.9 million rubles ($64,000) to victims with severe and moderate injuries, and 1 million rubles ($33,600) to those with minor injures.
Moscow's City Hall and the Moscow region, where Domodedovo is located, declared Wednesday a day of mourning. Both also opened bank accounts for donations to victims, they said on their web sites.