Iranian security forces have arrested eight foreign suspects after detaining a gunman in the killing of one person at a Shia Muslim shrine, state media reported on Monday.

The attack came less than a year after a mass shooting at the same holy site, the Shah Cheragh mausoleum in Shiraz, the capital of Fars province in Iran’s south.

“Eight people suspected of links with the terrorist attack… have been arrested,” according to the judiciary’s Mizan Online website, quoting Fars province chief justice Kazem Mousavi.

“All the people arrested are foreigners,” Mousavi said, without elaborating. The eight are in addition to the main suspect arrested on Sunday night after the attack. Mizan identified him as Rahmatollah Nowruzof from Tajikistan.

Sunday’s shooting wounded eight people, the official IRNA news agency reported.

Windows were left shattered by bullets, and blood stained the ground in a courtyard of the arched and collonaded complex after the shooting.

There was no immediate claim of responsibility but Fars provincial governor Mohammad Hadi Imanieh blamed the militant Islamic State group.

He told state TV that the assailant sought “to take revenge for the execution of two terrorists” convicted of carrying out the similar attack last year.

On Monday, Interior Minister Ahmad Vahidi told state TV during a visit to the site that the “terrorist” was collaborating with a “network operating” outside Iran.

On October 26, a mass shooting at the shrine left 13 people dead and 30 wounded. IS later claimed the attack.

Iran hanged two men in public on July 8 over the killings after their conviction for “corruption on earth, armed rebellion and acting against national security,” Mizan said at the time.

Three other defendants in the case were sentenced to prison for five, 15 and 25 years for being members of IS, according to Moussavi.

In November, Tehran said 26 “takfiri terrorists” from Afghanistan, Azerbaijan and Tajikistan had been arrested in connection with the mass shooting.

In Shia-dominated Iran, the term takfiri generally refers to jihadists or proponents of radical Sunni Islam.

The Shah Cheragh mausoleum is home to the tomb of Ahmad, brother of Imam Reza — the eighth Shia imam — and is considered the holiest site in southern Iran.

Last year’s shooting occurred as nationwide protests gripped Iran following the death in custody of Mahsa Amini, 22, arrested for an alleged breach of strict dress rules for women.