Peter Bergen is CNN's national security analyst, a vice president at New America and a professor of practice at Arizona State University. He is the author of " United States of Jihad: Investigating America's Homegrown Terrorists ."

(CNN) Wednesday's truck bomb in Kabul that killed at least 90 and injured 400 others augurs for what could be a deadly Ramadan, the holy Islamic month that began on Friday.

In the past, Ramadan was treated as a month for peace and tranquility. UN envoys world leaders and even rebel groups would call for cease-fires in their respective parts of the world.

But ISIS has other ideas. Though Ramadan is a month when the vast majority of Muslims are fasting and praying, ISIS asks its followers to commit heinous acts of terror.

This year was no different. ISIS called for attacks during Ramadan on a YouTube channel and in one of its popular webzines, Rumiyah.

And it seems like terrorists may be heeding ISIS' calls. In Egypt, on Friday, gunmen fired on a bus carrying Coptic Christians, killing at least 28. ISIS claimed responsibility for the attack.

And, on Tuesday, twin bombings in Baghdad killed at least 22. In an attack of special malevolence, one of the bombs detonated outside an ice cream parlor. CNN reported that most of the victims were women and children. ISIS also claimed responsibility for these bombings.

Now comes Wednesday's bombing in Kabul, a massive truck bomb that detonated in the city's downtown embassy district. Most of the victims, as is so often the case in these attacks, were ordinary Afghans, and the death toll, which now stands at 90, is expected to rise.

The Taliban have denied responsibility for the Kabul bombing, which may mean that ISIS was also behind this attack.

But if history is any lesson, these Ramadan attacks are unlikely to be confined to the Middle East and Asia.

In late May 2016, an ISIS spokesman called for attacks in the West during the month of Ramadan.

And less than a month later, on June 12, 2016, Omar Mateen killed 49 at a gay nightclub in Orlando, Florida. Mateen pledged allegiance to ISIS during his attack, the worst terror attack on American soil since 9/11.

Michael S. Smith II, an American analyst who carefully tracks ISIS propaganda, told me that ISIS' Nashir news service last week called for attacks in the West that were similar to ISIS' calls for such attacks last year.

These exhortations must be taken seriously.

This is especially the case around the 27th day of Ramadan, the "Night of Power," which is a particularly sacred for the world's Muslims as it was the time that the Prophet Mohammed started receiving the first verses of the Koran.

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In 2016, the 27th day of Ramadan fell on July 2. This is the same day that ISIS attackers in Bangladesh massacred 20 at a restaurant popular with foreigners in the capital, Dhaka.

The 27th day of Ramadan in 2016 was also the same day that ISIS launched a car bomb that killed more than 200 in Baghdad.

Security services from Afghanistan to the United States should be alert throughout the Ramadan period, but especially on the 27th day of the holy month.