ISTANBUL — The Islamic State issued a rare claim of responsibility Monday for the New Year’s Day attack on an Istanbul nightclub, which killed at least 39 people, describing the gunman who carried out the assault — and who has not been identified or captured — as a “soldier of the caliphate.’’

Turkish authorities are still searching for the gunman, who killed a police officer guarding the Reina nightclub before going on a shooting rampage with a rapid-fire rifle, leaving 39 dead, but the state news media reported that eight suspects had been detained in connection with the attack.

Late Monday, special operations police acting on a tip raided an apartment in the Zeytinburnu district of Istanbul but made no arrests, the Associated Press reported.

Authorities released two photographs of the suspected gunman, captured by security cameras, that showed a dark-haired, clean-shaven man in a dark winter coat. The government’s spokesman, Numan Kurtulmus, said investigators believed they found the assailant’s fingerprints and that they were close to identifying him.

Referring to the attack, which happened just after midnight Sunday morning, Kurtulmus said, “The fact that it was done during the first minutes of 2017 gives an important message. The message is, ‘We will go on to menace Turkey in 2017.’ And we say to them, we will break into your caves wherever you are.’’

ISIS asserted in a statement that the attack had been carried out “in continuation of the blessed operations that the Islamic State is conducting against Turkey, the protector of the cross.’’

“A hero soldier of the caliphate attacked one of the most famous nightclubs, where Christians celebrated their pagan holiday,’’ read the statement from the Islamic State, also known as ISIS or ISIL. “They used hand grenades and a machine gun and transformed their celebration to mourning.’’

In an apparent reference to Turkey’s role in the conflict in Syria, the statement warned that “the government of Turkey should know that the blood of Muslims, which it is targeting with its planes and its guns, will cause a fire in its home by God’s will.’’

The statement did not name the assailant, and it was not clear whether the Islamic State had organized the attack or had merely inspired the gunman. But the shooting came just days after a pro-Islamic State group, the Nashir Media Foundation, published the latest in a series of messages calling for attacks on clubs, markets, and movie theaters.

The state-run Anadolu news agency said that 38 of the 39 people who died in the attack on Sunday had been identified, the AP reported. At least two dozen of the people killed were said to be foreigners. Another 70 people were wounded.

The State Department said Monday that William J. Raak, 35, a small-business owner from Greenville, Del., was the only US citizen injured in the Istanbul attack. Raak told NBC News that he stayed silent and motionless even after being shot in a hip.

The Islamic State’s claim of responsibility came after years of complex relations between the Turkish state and the jihadi group operating across its southern border. Several terrorist attacks in Turkey over the last year have been attributed to the Islamic State, but the militant group rarely claims responsibility for major attacks in the country. A rare exception came in November, when the group claimed to be behind a car bombing in southeastern Turkey.

Analysts said the Islamic State has walked a fine line in Turkey, trying to balance its goal of destabilizing the country without antagonizing the government to the extent that it would crack down heavily.

For years, Turkey looked the other way, according to analysts and regional diplomats, as jihadi groups moved fighters and supplies across the border, establishing deep networks in Turkish border towns.

Committed to supporting the uprising against President Bashar Assad of Syria, Turkey felt the jihadis could be managed while they fought with forces loyal to the Syrian government.

But that policy ultimately changed, as Turkey worked to secure its borders, under pressure from its allies as it took in millions of Syrian refugees and as terrorist attacks rocked the country.

Turkey began a military intervention in northern Syria in August that put its forces on the front lines against Kurdish militants as well as Islamic State fighters. This turned the jihadis decidedly against Turkey.