Russia said it had detained a police colonel from Dagestan on terrorism offences after accusing him of aiding a suicide bomber in a 2010 attack on the Moscow metro.
Spencer Stone arrived in Paris, France, on Wednesday but was hospitalised upon arrival. He has now returned to the US, his lawyer confirmed on Sunday.
Sixteen people died in the attacks on Las Ramblas and in the coastal town of Cambrils.
On the fourth anniversary of the November 13, 2015 terror attacks, French government officials will commemorate the victims of the deadliest day witnessed in the French capital since World War II.
Tunisian Prime Minister Youssef Chahed has banned the wearing of the niqab in public institutions for security reasons, according to Reuters, citing an official source.
The death toll in Sri Lanka's Easter Day attack is around 100 fewer than the 359 originally thought, top government officials said on Thursday.
People gathered to hold a moment of silence in remembrance of the Easter Sunday's attacks at 08:30 am local
"They are believed to have agreed to carry out an Islamist terrorist attack using a vehicle and guns that would kill as many 'non-believers' as possible," prosecutors said.
"It was truly a murder attempt. There was blood everywhere," a trade union representative for prison guards said.