Moscow's Domodedovo airport has been rocked by a bomb explosion that an airport spokesman says has killed 35 people. More than 100 people were injured - 20 of them critically - by the blast, which reports suggest was the work of a suicide bomber. Russia's chief investigator said terrorists were behind the attack. The airport - the busiest serving Russia's capital - is 40km (25 miles) south-east of the city centre. President Dmitry Medvedev vowed those behind the attack would be tracked down. He ordered increased security across Russia's capital, its airports and other transport hubs, and called an emergency meeting with top officials. He also postponed his planned departure for this week's World Economic Forum at Davos. BBC security correspondent Gordon Corera said immediate suspicion about Monday's attack would fall on militants from the Caucasus region. Militant groups fighting in the Caucasus know how important the perception that the president and prime minister provide a secure society is, and to undermine that is a key aspect of their aims, adds our correspondent. Last March the Russian capital's underground system was rocked by two female suicide bombers from Russia's volatile Dagestan region, who detonated their explosives on the busy metro system during rush hour, killing 40 people and injuring more than 80. 'Almighty explosion' Reports suggest Monday's blast at Domodedovo hit the international arrivals hall - which was packed as several international flights had just landed - creating a cloud of smoke. The device is thought to have contained the equivalent of 7kg (15lb) of TNT. "The explosion occurred in the international arrivals hall in a public area, to which people who are not passengers have free access," airport spokeswoman Yelena Galanova told Interfax news agency. According to eyewitnesses quoted by Russian TV's Vesti news programme, before detonating the explosives the bomber shouted: "I'll kill you all!" Briton Mark Green, who was on a British Airways flight that landed at the airport before the explosion, told BBC News there were thousands of people in the baggage collection area, baggage hall and queue for immigration at the time of the blast. "We were walking out through the exit of the arrivals hall towards the car, and there was this almighty explosion, a huge bang... my colleague and I looked at each other and said 'Christ that sounds like a car bomb or something,' because the noise was, literally, it shook you," Mr Green told BBC News. He described scenes of panic and how he gave a drink of water to a bloodied Russian man whose face was blackened with soot. After the blast, the dead and wounded were moved around the area on luggage trolleys. In the aftermath of the explosion, Mr Medvedev told Russian state television a commission of inquiry would be established "to conduct urgent on-the-spot investigations". He said: "After previous similar events, we passed appropriate legislation, and we have to check how it has been applied. Because obviously there have been lapses, and we have to get to the bottom of this." Police are hunting for three suspects in connection with the bombing, Russian media report. All flights from Domodedovo have been suspended since the blast, while incoming flights are being diverted to Moscow's Sheremetevo airport. US President Barack Obama has condemned what he called an "outrageous act of terrorism", while Nato has sent a message of solidarity to Russia's government. EU President Herman Van Rompuy called for those behind the attack to be punished, and UK Foreign Secretary William Hague sent the condolences of the British government to all those who had lost relatives or been injured. "British officials are in urgent contact with the Russian authorities to establish the facts and to provide consular support to any British nationals who may have been affected," said Mr Hague. Source: BBC