ISTANBUL -- The Islamic State of Iraq and Syria (ISIS) claimed Monday to have been behind the attack on a popular Istanbul nightclub during New Year’s celebrations, as new video emerged showing the gunman opening fire about an hour into 2017.

In the new video, which emerged Sunday on social media, the still-unidentified gunman is seen approaching the Istanbul nightclub with a rifle.

ISIS claimed responsibility for the nightclub attack issuing a vague statement on their own Amaq news portal saying “a security source” had told them “a fighter of the Islamic state” was behind the carnage. The statement followed a similar pattern to claims issued after previous attacks carried out by people with loose affiliations with the group.

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The Amaq claim greatly exagerated the death toll from the attack, and offered no proof that the attacker had prior connections to ISIS. It noted, however, that ISIS “has called upon its supporters and fighters to launch attacks against Turkey, which has entered into the cycle of conflict against the Islamic state.”

Deputy Prime Minister Numan Kurtulmus on Monday confirmed news reports that said eight people were taken into custody but did not provide details, saying a “sensitive” investigation was underway.

Authorities had obtained the fingerprints and a basic description of the gunman and were close to identifying him, Kurtulmus said.

The gunman, who escaped after carrying out the attack, wasn’t among the eight arrested.

Surveillance footage from Turkish news agency IHA shows the Istanbul shooter at a money exchange venue sometime before he attacked the nightclub Reina. CBS News

Turkish newspapers Hurriyet and Karar reported Monday, citing unnamed security officials, that authorities have determined the gunman who killed 39 people comes from a Central Asian nation and is believed to be either from Uzbekistan or Kyrgyzstan.

Kyrgyzstan’s Foreign Ministry said it is looking into reports that the gunman could be from the Central Asian country. Ministry spokeswoman Aiymkan Kulukeyeva was quoted as saying Monday by the Interfax news agency: “According to preliminary information, this information is doubtful but we are checking all the same.”

Turkey’s Interior Ministry said that dozens of people have been detained in the past week over suspected ties to ISIS.

In a statement released Monday, the ministry said 147 people were detained after authorities determined “they were in contact with the Daesh terrorist organization,” referring to an Arabic acronym for ISIS.

Of the detained, 25 people have been formally put under arrest.

Police have established similarities with the high-casualty attack at Ataturk Airport in June and were investigating whether the same ISIS cell could have carried out both attacks.

The gunman, who is still at large, killed a policeman and another man outside the Reina club in the early hours of 2017 before firing at people partying inside.

Turkey’s state-run news agency said a criminal complaint has been filed against people who used social media to praise the deadly New Year’s attack at a nightclub in Istanbul, as well as against several people who demonized the New Year celebration or threatened attacks.

The Turkish Bar Association filed a criminal complaint with the Ankara Chief Public Prosecutor’s office on Monday, calling for the investigation and prosecution of those who praised the gun attack which killed 39 and injured dozens.

Some social media users praised the killings and condemned the night’s celebration on religious grounds.

The complaint also called for prosecution of a school administrator who banned New Year’s celebrations, those responsible for protests or banners depicting violence against Santa Claus, as well as a newspaper which published threatening headlines.

Prime Minister Binali Yilidirim sent a Twitter message on Sunday warning that legal action would be taken against those who praised terrorism.

Nearly two-thirds of the dead in the upscale club, which is frequented by local celebrities, were foreigners, Turkey’s Anadolu Agency said. Many of them hailed from the Middle East.

Citing Justice Ministry officials, Anadolu reported that 38 of the 39 dead have been identified. The report said 11 of them were Turkish nationals, and one was a Turkish-Belgian dual citizen.

The report says seven victims were from Saudi Arabia; three each were from Lebanon and Iraq; two each were from Tunisia, India, Morocco and Jordan. Kuwait, Canada, Israel, Syria and Russia each lost one citizen.

The U.S. State Department confirmed Sunday evening that one American was injured in the attack, and the man’s family has identified him as William Jacob Raak.

A Delaware businessman originally from Chadds Ford, Pennsylvania, he was one of nearly 70 people wounded during the New Year’s Eve celebration in Istanbul.

CBS Philadelphia spoke to Raak’s brother Chris, who said Jake was shot, but the bullet hit his cell phone and ricocheted off his phone, into his leg.

Raak then laid still, pretending to be dead while the gunman continued to roam the club.

Chris Raak said that the family was relieved his brother had only suffered a minor leg injury and that he would be coming home. He said they were praying for the other victims and their families.

Jake Raak was recovering from his injury at an Istanbul hospital and was listed in stable condition, according to CBS 3.

The mass shooting followed more than 30 violent acts over the past year in Turkey, which is a member of the NATO alliance and a partner in the U.S.-led coalition fighting against ISIS.

The country suffered multiple bombings in 2016, including three in Istanbul that authorities blamed on ISIS, a failed coup attempt in July and renewed conflict with Kurdish rebels in the southeast.