The terror group ISIS is calling upon its adherents to carry out terrorist attacks in the major Western cities of San Francisco, New York, and London, according to several social media posts monitored by an ISIS watchdog site.

An ISIS media wing posted the terror advertisements on the Telegram networking website, telling followers to "answer the call" and warning ISIS opponents that attacks would happen "immediately" in their countries, the Middle East Media Research Institute reported.

"The pro-Islamic State (ISIS) Ash-Shaff Media Foundation shared five posters on Telegram which threaten and encourage terror attacks in the West," according to posts gathered by MEMRI. "The posters are captioned in poor English and feature background images of San Francisco, New York City, and London. The Ash-Shaff media group is believed to be based in Indonesia and/or operated by Indonesians."

One poster featuring what appears to be New York tells adherents to "go and answer the call."

"Don't spare none [sic]. Kill them all. It is now time to rise. Slit their throats. Watch them die," the poster read.

Another poster depicts a man with a backpack on and a suicide bomb attached to himself standing in front of a taxi.

"Through our blood comes success and well [sic] give it our best to destroy the Kuffar. We will slaughter them all," read the caption on the post.

A third post displays a burning backdrop of London, with several buildings engulfed in flames, including the Palace of Westminster and Big Ben.

"O Crusaders in London and everywhere," the caption read, which MEMRI reported is a phrase commonly used to refer to the enemies of ISIS. "Do you think we have failed? Do you think the supports of the Islamic State gonna [sic] be surrender? Be know [sic], O Crusaders, the soldiers of [sic] caliphate is everywhere and will attack immediately in your countries."