The Islamic State (ISIS/ISIL) has claimed responsibility for the terrorist attack in Bangladesh that killed at least 20 hostages, but some officials doubt the jihadist group carried out the massacre.

A senior minister in Bangladesh claims the attackers were members of a homegrown Bangladeshi jihadist outfit.

Meanwhile, an unnamed U.S. official suggested to CNN while the attack was ongoing that the culprits may be linked to al-Qaeda in the Indian Subcontinent (AQIS), which is known to operate in Bangladesh.

Local police have reportedly said that two officers were killed in addition to at least 20 people who were taken hostage during the nearly 10-hour standoff at the Holey Artisan Bakery cafe in Dhaka that began the night of July 3 and carried into the next day. An estimated 40 people were also reportedly wounded.

“Most of them had been brutally hacked to death with sharp weapons,” reportedly said Brig. Gen. Nayeem Ashfaq Chowdhury, a Bangladesh Army spokesman, referring to the fatalities.

A group of Bangladeshi gunmen stormed the cafe, which is popular with foreigners, and opened fire as they screamed “Allahu Akbar” around 9 p.m. on July 3, according to witnesses.

Bangladesh’s Home Minister Asaduzzaman Khan told several news outlets that the attackers belong to an outlawed domestic group known as Jamaat-ul-Mujahideen Bangladesh (JMB) and “have no connections with the Islamic State.”

JMB and Ansar-al-Islam, which has been linked to the local al-Qaeda branch AQIS, are reportedly the two most prominent jihadist groups in Bangladesh.

“Of the two, Ansar, which pledges allegiance to al Qaeda, has emerged as the most organized and dangerous, they say, while Jamaat-ul-Mujahideen is seen as a looser organization that claims it represents Islamic State but has no proven links to it,” reports Reuters.

In the midst of the hostage-taking attack in Dhaka, an unnamed U.S. official told CNN that AQIS was likely the terrorist group behind the massacre.

CNN learned from the official that “based on past operations, it is more likely that al Qaeda in the Indian Subcontinent conducted this attack.”

“While this was a preliminary assessment based on information developing at the time, the official says AQIS has demonstrated a more capable presence in Dhaka over the past few months than ISIS,” noted the news network amid the attack. “So far, all its attacks in Bangladesh have been in the capital.”

CNN now reports, “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.”

Although the senior Bangladeshi minister, Khan, believes the attackers are not associated with ISIS, local police are looking into the possibility that the terrorists may indeed be affiliated with the jihadist group, reports USA Today.

Both ISIS and AQIS have been linked to a spate of attacks in Bangladesh over the past 18 months, often involving jihadists using machetes, against individuals including writers, bloggers, academics, activists, liberals, atheists, foreigners, gays, and religious minorities.

The attacks have occurred despite a nationwide government crackdown on militants that has resulted in the arrest of more than 14,000 people.

ISIS has reportedly assumed responsibility for more than half of the 48 killings in Bangladesh that have been blamed on jihadists in the last 18 months. AQIS has claimed responsibility for most of the others.

“We now have competition between al Qaeda and the Islamic State in Bangladesh, which means that the jihadist pool is deep enough for both organizations to operate in the country,” Thomas Joscelyn, senior editor at The Long War Journal that tracks jihadi organizations across the world, told Reuters.

AQIS was officially designated a foreign terrorist organization by the United States the day before the Dhaka attack.