By Ruma Paul

DHAKA (Reuters) - Bangladeshi investigators poring over CCTV footage believe they have spotted four new suspects, including a woman, involved in a bloody attack on a cafe in the capital, Dhaka, this month, a senior security official said on Tuesday.

Twenty-two people were killed in the attack, most of them foreigners, after five young Bangladeshi men stormed into the restaurant in an upscale part of the capital in an assault claimed by Islamic State.

The five men were all killed hours later when security forces battled their way into the cafe to end the siege.

Authorities have detained at least two people for questioning in connection with the attack and an official from the elite, police-run Rapid Action Battalion (RAB) said accomplices of the attackers might have been detected.

"We have detected four new suspects after assessing CCTV footage. We are now working to identify them,” the RAB’s Legal and Media wing chief Mufti Mahmud Khan told Reuters.

The footage was taken outside the cafe popular with foreigners before the July 1 attack, he said.

In the video, the suspects were seen walking on the pavement and road and a "suspicious" car was also seen on the road.

The security force posted a video of the footage on its Facebook page - https://www.facebook.com/rabonlinemediacell/ - and appealed for anyone with information about the people shown to come forward, Khan said.

The attack was one of the deadliest militant attacks in Bangladesh, where Islamic State and al Qaeda have claimed a series of killings of liberals and members of religious minorities in the past year.

Police believe that Jamaat-ul-Mujahideen Bangladesh, an outlawed domestic group that has pledged allegiance to Islamic State, played a significant role in organizing the group of privileged, educated young men who carried out the attack.

The attack marked a major escalation in violence aimed at forcing strict Islamic rule onto predominantly Muslim Bangladesh.

Nine Italians, seven Japanese, an American and an Indian were among the dead. Two Bangladeshis were also murdered inside the restaurant while two police officers were killed outside during the standoff.

(Reporting by Ruma Paul; Editing by Robert Birsel)