The Islamic State group is extending its reach in Saudi Arabia, expanding the scope of its attacks and drawing in new recruits with its radical ideology. Its determination to bring down the U.S.-allied royal family has raised concerns it could threaten the annual Muslim hajj pilgrimage later this month.

So far, the group’s presence in the kingdom appears to be in a low-level stage, but it has claimed four significant bombings since May, one of them in neighboring Kuwait. And it has rapidly ramped up its rhetoric, aiming to undermine the Al Saud royal family’s legitimacy, which is rooted in part in its claim to implement Islamic Shariah law and to be the protectors of Islam’s most sacred sites in Mecca and Medina that are at the center of hajj.

“Daesh and its followers have made it very clear that Saudi Arabia is their ultimate target,” Saudi analyst Fahad Nazer said, referring to the Islamic State group by its Arabic acronym. “Because of Mecca and Medina … That’s their ultimate prize.”

An attack last month in which IS claimed responsibility appeared to mark a significant spread in the group’s reach. Militants claiming loyalty to the group had already carried out three major bombings — two in eastern Saudi Arabia in May and one in Kuwait City in June, all targeting Shiite mosques and killing 53 people.

But on Aug. 6, a suicide bomber attacked in western Saudi Arabia, hitting a mosque inside a police compound in Abha, 350 miles south of Mecca, killing 15 people in the deadliest attack on the kingdom’s security forces in years. Eleven of the dead belonged to an elite counterterrorism unit whose tasks include protecting the hajj pilgrimage.

The alleged affiliate that claimed responsibility for the August attack called itself the “Hijaz Province” of the Islamic State, its first claim of a branch in the Hijaz, the traditional name for the western stretch of the Arabian Peninsula where the holy cities are located. The previous attacks were claimed by the group’s “Najd Province,” the traditional name for the central heartland of the peninsula and the homeland of the Al Saud family.

Lori Boghardt, Gulf security analyst at the Washington Institute, said it would not be surprising if IS radicals tried to take advantage of the hajj to stage an attack, particularly since the group has encouraged lone wolf operations. This year, the hajj begins Sept. 21 and is expected to draw some 3 million Muslims from around the world.

“The kingdom is a holy grail of sorts as a target from the perspective of ISIS because of its significance to Muslims,” she said, referring to the group by its longer acronym.

A direct attack on pilgrims carrying out the hajj rites — potentially causing large casualties or damaging holy sites — may be a risky move for IS, bringing a backlash from shocked Muslims worldwide. Still, the group “has made it very clear they have no red lines,” said Nazer, a senior analyst at the Virginia-based consultancy and security firm JTG Inc.

But there are other potential targets, including security forces in or around Mecca. The group could attempt to hit pilgrims from Shiite-majority nations like Iran, who would stand out since pilgrims generally move in groups by country. IS and other Sunni radicals consider Shiites heretics. ABC News