TUNIS, Tunisia (AP) -- Eight people are in custody on suspicion of direct links to a deadly attack on a Tunisian beach resort, while police have released four others detained earlier in the investigation, a government minister said Thursday.
Meanwhile, the British Foreign Office raised the death toll of British tourists killed in the attack from 27 to 30. Other European tourists were among the 38 dead.
The Islamic State group claimed responsibility for Friday's attack, in which Tunisian student Seifeddine Rezgui opened fire on a beach in the resort of Sousse. The attacker was later killed by police.
Government minister Kamel Jendoubi told reporters in Tunis on Thursday that 12 people in total were detained since the attack, but four have been released.
The other eight — seven men and one woman — remain in custody and are suspected of direct links to the attack, he said.
He did not elaborate on the identities of the suspects or their roles, saying only that the investigation "has allowed us to discover the network behind the operation in Sousse."
He also urged greater international terrorism cooperation in a "war ... between democratic Tunisia and an international jihadi movement."
More Tunisians — about 3,000 — are believed to have gone to Syria and Iraq to join radical jihadis including the Islamic State group than fighters from any other country.
A top security official told the AP this week that the student had trained in a jihadi camp in Libya at the same time as the two men who attacked a leading Tunisian museum in March. That enforced the notion of a link between the two assaults and raised fears of more attacks on this North African nation's budding democracy.
The attack was Tunisia's deadliest ever, and threatened to be a devastating blow to the country's tourism sector.