10:14, 04.Aug 2016
Seven were detained in Brussels, two reportedly in Germany and one in Paris.
An investigation is continuing into Tuesday's bomb attacks, which killed 31 people in Brussels and have been linked to November's Paris attacks.
Explosions have been reported in the Schaerbeek suburb of Brussels as a police operation continues.
Media reports said a man had been "neutralised" during the operation, and an area was sealed off by heavily armed police and military vehicles.
Schaerbeek is one of the districts where arrests were carried out on Thursday.
US Secretary of State John Kerry, visiting Brussels, said that so-called Islamic State (IS) would be destroyed.
Standing alongside Belgian Prime Minister Charles Michel, he expressed condolences for the victims and solidarity with Belgium, declaring "Je suis Bruxellois".
The Western alliance would continue its fight to destroy IS, Mr Kerry said.
"We will not be intimidated. We will not be deterred."
Details of further arrests have been emerging:
-Brussels: Six detained in the Schaerbeek and Jette districts, and the city centre. Media reports seventh suspect seized in the Forest district.
-Paris: Reda Kriket, 34, arrested in Paris' north-western Argenteuil suburb, alleged to be in the "advanced stage" of plotting an attack. 2015 Brussels court conviction for IS recruitment, along with Paris attacks ringleader Abdelhamid Abaaoud.
-Germany: Two suspected jihadists detained in Dusseldorf and Giessen areas on Wednesday and Thursday - both with suspected links to one of the Brussels bombers, Der Spiegel reports, and one with suspicious text messages on his mobile phone referencing Brussels.
More details of those killed in the Brussels attacks have been released. Nationals of 40 countries were caught up in the attacks.
Among the deaths confirmed so far:
-Three Dutch citizens
-One Briton, David Dixon
-One Chinese national
The Brussels bombings continue to have political repercussions, which questions surrounding the issue of whether more could have been done to prevent them.
Turkey has said it arrested and deported one of the bombers, Brahim el-Bakraoui last June, warning Belgium he was a "foreign fighter" - but the message was "ignored". The Dutch authorities had also been alerted, Ankara said.
Bakraoui is one of three men who carried out the bombings at Brussels airport, killing 11 people.
The Belgian interior and justice ministers said they had offered their resignations but the prime minister refused to accept them.
The other two airport attackers have not yet been identified. Bakraoui's brother, Khalid, struck at Maelbeek metro station, where 20 people died.
There are reports of a second suspect being sought for that attack. One source told AFP news agency that a man with a large bag had been seen beside Khalid el-Bakraoui on surveillance footage at the metro station.
Meanwhile, the Flemish-language public broadcaster VRT reported that investigators were working on the assumption that the cell had been planning a far bigger attack, involving Paris-style shootings as well as suicide bombings.
Links have also emerged with Salah Abdeslam, a suspect in the Paris attacks.
Abdeslam was arrested and wounded in a police raid on a flat in Brussels last Friday - four days before the attacks in the Belgian capital.
Investigators say Khalid el-Bakraoui used a false name to rent the same flat.
Source : BBC