U.S. military officials on Friday denied reports that the U.S.-led military coalition overseeing operations in Iraq and Syria launched a Special Operations raid in the Islamic State’s stronghold, following a burst of claims from activists in the region.

Media reports raising the possibility of an attempted raid in Raqqa surfaced after a group known as “Raqqa is Being Slaughtered Silently” detailed what it described as two failed approaches by coalition aircraft. The organization said in an English-language report that the city “witnessed an unusually intense aerial campaign” by coalition fighter jets on Thursday, and that helicopters “attempted to make an airborne-landing operation to free and rescue western hostages captured by ISIS in the eastern Raqqa countryside,” using one of the acronyms for the Islamic State militant group.

“The mission failed when the helicopters were met by ISIS fighters who directly opened fire at them forcing them to take off,” the activist group said.

One of the activists, Abu Ibrahim al-Raqqawi, said in an interview from Turkey that eyewitnesses about 15 miles east of Raqqa heard intense aerial drone activity Thursday night. The sky was lit up brightly with gunfire and illuminated with flares, and two helicopters attempted to land around 11:30 p.m., the activist said.

Afterward, militants took to the streets throughout Raqqa and set up multiple checkpoints, he added.

Officials at the Pentagon and with the U.S.-led military coalition carrying out operations against the Islamic State denied the reports. Rear Adm. John Kirby, the Pentagon press secretary, said there was no ground operation or other form of raid involving U.S. Special Operations troops.

Army Maj. Neysa N. Williams, a spokeswoman for Combined Joint Task Force-Operation Inherent Resolve, said officials with her unit were aware of the speculation, but had no information about it. But she added that if any operation was undertaken by the United States or a coalition partner, it would have been coordinated through the task force.

Raqqa is Being Slaughtered Silently is made up of Syrian activists who monitor Islamic State activities in the city, its de facto capital. They have been responsible for exposing many of the human rights violations that have taken place, such as beheadings and other executions, posting videos and photographs on their Facebook page.

The group was the first to report the failed July 3 rescue attempt of U.S. hostages at a location east of Raqqa — not far from the site where helicopters were said to have tried to land on Thursday. Although the report received little attention at the time, the rescue attempt was confirmed by U.S. officials in August, after the first U.S. hostage, James Foley, was beheaded by the Islamic State.

A U.S. official said at the time that they intended to keep that operation secret, but went public with the information after it became clear that a number of media organizations planned to report on it.

In this case, activists said they were basing their reports on Islamic State contacts who claimed to have seen two helicopters attempt to land nearby. The activists concluded the activity east of Raqqa indicated there had been an attempted raid.

Militants in Syria have numerous Western hostages. Most recently, the al-Qaeda linked Jabhat al-Nusra distributed a video earlier this week showing two Italian women who were kidnapped in northern Syria this summer. The Islamic State also captured a Jordanian pilot in December after his warplane crashed while making a bombing run in Syria.

The Daily Mail newspaper of Britain reported Friday that U.S. Special Forces were forced to abort a raid attempt to recover the pilot, but Kirby specifically denied that occurred. It isn’t clear if the Jordanians may have run an independent operation trying to get the pilot back.

Liz Sly contributed to this report.