Moscow (CNN) -- Terrorists detonated a bomb at Moscow's busiest airport on Monday, killing 35 people and wounding 152, Russian authorities said.
President Dmitry Medvedev, who called the bombing a terrorist attack, ordered additional security at airports and transportation hubs around the country, 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.
The Russian National Anti-Terrorist Committee said 35 people were dead and 152 had been wounded in the explosion.
State TV, citing Russian authorities, said the bombing 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 waiting for arriving passengers. CNN could not independently verify those claims.
A heavy police presence remained outside the airport nearly four hours after the explosion, and more than 10 ambulances left the airport with lights flashing and sirens screeching.
Incoming flights scheduled to land at Domodedovo were being diverted to Moscow's other airports, Sheremetyevo and Vnukovo, Russian TV said.
However, airport spokeswoman Yelena Galanova told Russian state TV that the airport was "operating as usual."
"There have been no departure delays. We were shut for only about 20 minutes after the explosion," she told state TV.
An airport employee, Andrei Surkov, told CNN that while the international arrivals area is still closed, international passengers were being routed through the domestic terminal located on the other end of the airport.
Lufthansa spokeswoman Claudia Lange said the airline has suspended all flights to Domodedovo until further notice.
Elina Bakhtina told state TV she was at the airport cafe she owns when the explosion occurred.
"The blast must have been very strong, because our cafe is about 100 meters from the arrivals area. When we heard the blast, glass just started falling from the ceiling," she said.
31 dead in Moscow airport explosion
Tatyana Papova, who was waiting at passport control when the explosion occurred, told state TV that escalators stopped working at the baggage claim area and airport employees started breaking down walls to help clear people from the area.
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.
U.S. President Barack Obama called the bombing a "premeditated attack against innocent civilians."
State Department spokesman P.J. Crowley said the U.S. government had no information that any Americans were injured.
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."
NATO Secretary General Anders Fogh Rasmussen condemned the attack and urged greater cooperation in the fight against terrorism.
German, French, and Isreali leaders also condemned the attacks.
Will Geddes, terrorism expert and managing director of International Corporate Protection Group, called the bombing a "very significant terror strike."
"To strike in the airport -- which is fundamentally believed and understood by many to be one of the most secure types of installations in a city or in a country -- to have such a devastating an attack with such a tragic result, means that they had planned this considerably well and gone ahead in achieving their aims," he said.
Russia has a long history of dealing with terror attacks.
In 2004, two airplanes that took off from Domodedovo exploded, killing at least 89 people in an attack blamed on Chechen suicide bombers.
More 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. Chechen rebels claimed responsibility for that attack.
In November 2009, an explosive device derailed an express train, killing at least 26 people.
CNN's Maxim Tkachenko contributed to this report