ISIS claims attack

ISIS claimed responsibility for the attack in a statement.

Initially, a U.S. official told CNN it was more likely that al Qaeda in the Indian Subcontinent conducted this attack because it had demonstrated a more capable presence in Dhaka through attacks over the past few months. But after photos purportedly showing the inside of the cafe and dead hostages were posted on an ISIS-affiliated website, U.S. officials said they are now focused on ISIS as the perpetrator.

Bangladeshi army: 'Sharp weapons' used to kill hostages 01:55

The photos were posted on Amaq while the siege was ongoing, with a claim that the extremely graphic images were of foreigners killed by terrorists in the attack.

The fact that the images were posted approximately 90 minutes before Bangladeshi forces stormed the restaurant suggest that several hostages had already been killed before the commandos moved in. While CNN can't verify the authenticity of the photos, the images show wall murals, glossy tables with carved legs, white chairs and other items very similar to those seen on the cafe website.

These photos don't prove that ISIS had operational control of the attack, but the website also displayed the photos and noms de guerre of five individuals, claiming they carried it out.