Secretary of State John Kerry bowed to congressional pressure Thursday, declaring that the Islamic State is conducting genocide against Yazidis, Christians and Shiite Muslims.

The declaration follows Monday's unanimous U.S. House of Representatives vote also calling ISIS's slaughter of religious minorities genocide. Congress previously gave Kerry until today to make a determination whether the Islamic State's actions qualified. ISIS "is genocidal by self-proclamation, by ideology, and by actions – in what it says, what it believes and what it does," Kerry said. "Daesh [ISIS] is also responsible for crimes against humanity and ethnic cleansing directed at these same groups and in some cases against Sunni Muslims, Kurds and other minorities."

Kerry noted specific atrocities carried out by Islamic State forces, including executing Christians solely based on their religion in Mosul and Qaraqosh in Iraq; murder of Coptic and Ethiopian Christians in Libya; and the systematic destruction of the cultural heritage of Armenian, Syriac Orthodox and Roman Catholics by blowing up their monasteries and churches.

Kerry also cited the ISIS murder of hundreds of Yazidi men in the town of Kocho, Iraq and its trapping of tens of thousands of Yazidis on Mt. Sinjar in Northern Iraq. The group subsequently captured thousands of Yazidis women and girls, enslaving them and raping them.

He additionally noted the Islamic State's frequent attacks against Shiites, who it calls "disbelievers and apostates."

"We know that Daesh's actions are animated by an extreme and intolerant ideology that castigates Yazidis as quote, 'pagans' and 'devil worshippers,' and we know that Daesh has threatened Christians by saying that it will, quote, 'conquer your Rome, break your crosses and enslave your women," Kerry said.

Former U.S. Rep. Frank Wolf, who was among the first to publicly call for such a declaration last year, expressed his gratitude to Kerry.

"I am very appreciative that they declared it," Wolf said. "It is very, very important."

Declaring the Islamic State responsible for genocide honors the victims, Wolf said. It makes it easier for Christians, Yazidis, Shiites and other groups covered by the declaration to obtain asylum.

Wolf also believes it could make Saudis, Qataris and Turks who have been complicit in supporting the Islamic State subject to prosecution.

"Now they are complicit in genocide," Wolf said. "It's important because in 2003 there were one and a half million Christians in Iraq. Now, they are down to 250,000. There was a group out of England ... that put out a report that said that if something isn't done there will be no Christians left in the Middle East."