Authorities in Belgium are searching for a third suspect after terror attacks on Brussels airport and a subway station killed 34 people and injures dozens of others.
Police carried out raids into the night and circulated a photo of three men seen in Zaventem Airport suspected of involvement in Tuesday's bombings.
Belgian state broadcaster RTBF has identified two of the attackers as brothers Khalid and Brahim El Bakraoui. They are believed to have blown themselves up.
The third man is at large and has not been identified.
The RTBF report on Wednesday said the brothers were known to police for past crimes, but nothing relating to terrorism. The broadcaster said Khalid El Bakraoui had rented an apartment which was raided by police last week in an operation that led authorities to top Paris attacks suspect Salah Abdeslam.
Last week, Belgian police said they were hunting for a suspected Abdeslam accomplice, Najim Laachraoui. He is believed to have made the suicide vests used in the November attacks in Paris, in which 130 people were killed, according to a French police official who said Laachraoui's DNA was found on all of them and in a Brussels apartment where they were made.
The airport and several Brussels metro stations remain closed on Wednesday. Security forces stood guard around the neighborhood housing headquarters of European Union institutions, as nervous Brussels residents began returning to school and work under a misty rain.
The Islamic State group claimed responsibility for the attacks and warned of more strikes against anti-IS allies.
It issued a communique promising "dark days" for countries taking part in the coalition against the terror group.
Meanwhile, the US military said it had launched an air strike in Yemen against the branch of al Qaida responsible for the attacks in France that killed 12 people at the Charlie Hebdo satirical magazine in January.
A tribal member at the site said about 40 people were killed or wounded in the Brom Maifa district.
Pentagon spokesman Peter Cook said the mountain training camp was being used by more than 70 terrorists belonging to al Qaida in the Arabian Peninsula.
Yemeni security officials and a witness said the air strike hit a former military base that had been taken over by al Qaida militants about 47 miles west of the terror group's stronghold city of Mukalla.
"We continue to assess the results of the operation, but our initial assessment is that dozens of AQAP fighters have been removed from the battlefield," Mr Cook said.
"This strike deals a blow to AQAP's ability to use Yemen as a base for attacks that threaten US persons and it demonstrates our commitment to defeating al Qaida and denying it safe haven."
Yemen has been left fragmented by war pitting Shiite Houthi rebels and military units loyal to a former president against a US-backed, Saudi-led coalition supporting the internationally-recognised government.