Turkish intelligence officials, nearly three weeks before Istanbul fell victim to multiple suicide bombings linked to the Islamic State (ISIS/ISIL), alerted the government about a potential terrorist attack by the jihadist group targeting the historic city, reports a senior Ankara-based journalist.

Hande Fırat reported that “intelligence units sent a warning letter to all state institutions about a possible attack on Istanbul,” according to Hurriyet Daily News.

“Intelligence units sent a warning letter to the top of the state and all its institutions in early June, around 20 days ago, about Istanbul,” she reportedly said.

The Istanbul Atatürk Airport, home to Tuesday’s jihadist massacre that left 42 people dead and at least 239 wounded, was listed in the correspondence among other potential ISIS targets, she added.

Firat is identified as a reporter for private broadcaster CNN Türk, owned by Doğan Media Group. She made the claims about the warning letter during a live broadcast on June 29.

U.S. Department of Homeland Security (DHS) Jeh Johnson told the Senate Judiciary Committee Thursday that an American citizen was among the foreigners injured in the attack in Istanbul.

“Thirteen of the victims were foreign including five Saudi Arabian nationals, one Tunisian, one Uzbek, two Iraqis, one Jordanian, one Ukrainian, one Iranian and one person of East Turkestan origin,” notes Hurriyet.

“The Turkish Prime Ministry declared an official day of mourning on June 29 due to the losses suffered in the attack,” it adds.

Although no one has yet to claim responsibility for the attack, the DHS chief and CIA Director John Brennan have indicated that the massacre has the earmarks of strikes by ISIS.

Brennan warned that similar attacks may take place in the United States.

Meanwhile, Johnson, echoing some experts, urged Americans Thursday to remain vigilant at all public places during the upcoming holiday weekend and on the Fourth of July, which falls on the day before the end of the Muslim holy month of Ramadan.

Martyrdom and engaging in jihad are especially valued and encouraged by radical Islamic extremists during Ramadan, and this year is not an exception.

ISIS has urged Muslims to attack wherever they can.

Tuesday’s assault is just the latest in a spate of deadly incidents that have taken place during the holy month in an apparent response to ISIS’ call to arms.

Since Ramadan began on June 5, Islamic terrorists have carried out attacks in Orlando, Afghanistan, Kenya, Lebanon, and now, Istanbul, Turkey.