MOSCOW (CNN) -- The explosion that killed at least 31 people Monday at Moscow's busiest airport appears to be an act of terrorism, Russian President Dmitry Medvedev said on state TV.
Medvedev ordered additional security at Moscow's other airports and transportation hubs, and Moscow police went on high alert in case of additional bombs.
The explosion occurred about 4:30 p.m. at the entrance of the international arrivals section of Domodedovo Airport, Itar-Tass said, citing a spokeswoman for the Russian Investigative Committee, Tatyana Morozova.
State TV aired video of the smoke-filled terminal, including what appeared to be bodies and luggage on the ground.
Russian state TV, citing Russian authorities, said the explosion was the act of a suicide bomber who stuffed a homemade bomb with small metal objects to make it more deadly, then activated it in a crowded area where many people were preparing for their flights. CNN could not independently verify those claims.
Incoming flights scheduled to land at Domodedovo were being diverted to Moscow's other airports, Sheremetyevo and Vnukovo, Russian TV said.
Lufthansa spokeswoman Claudia Lange said the airline has suspended all flights to Domodedovo until further notice.
Domodedovo is 22 kilometers (14 miles) southeast of Moscow. According to the airport's website, it is the largest of Moscow's three airports, as well as the busiest in terms of passenger traffic.
NATO Secretary General Anders Fogh Rasmussen condemned the attack and urged greater cooperation in the fight against terrorism.
British Foreign Secretary William Hague said British officials are "in urgent contact with Russian authorities to establish the facts and to provide consular support to any British nationals who may have been affected."
Russia has a long history of dealing with terror attacks.
Most recently, female suicide bombers struck the Moscow metro during rush hour in March, setting off two explosions that killed at least 38 people and wounded more than 60 others. Chechen rebels claimed responsibility for that attack.
In November 2009, an explosive device derailed an express train, killing at least 26 people.