DHAKA, BANGLADESH:  Police said Tuesday they were investigating an email sent to various media outlets reportedly by a banned Islamist group in Bangladesh threatening to topple "towering buildings" and telling the media not to run anything that goes against what the mail describes as jihad.

The email — sent after a series of deadly attacks targeting moderates and foreigners — contains a six-point directive that includes telling women to stay at home.

The letter sent Monday to Bangladeshi media was signed by the group Ansarullah Bangla Team, which is allegedly linked with several groups that claimed responsibility for killing four atheist bloggers this year. The Associated Press was not one of the recipients.

Authorities said they were taking the threat seriously and were investigating. "Higher authorities have been informed," Dhaka police spokesman Muntasirul Islam told reporters Tuesday.

The email has renewed concerns about radical forces within Bangladesh. Earlier this month, two foreigners — an Italian aid worker and a Japanese agricultural worker — were gunned down in daylight attacks five days apart. Responsibility for both of those attacks was claimed by the Sunni radical group Islamic State, but the Bangladesh government rejected those claims along with any suggestion the IS was active in the South Asian country.

The threatening email is signed with the name Abdullah bin Salim, who claims to be an Ansarullah spokesman. Authorities determined it had been sent from a computer in the southeastern district of Chittagong, according to local media that received the email threat including news service bdnews24.com and the Dhaka Tribune newspaper. Ansarullah also allegedly has ties with al-Qaeda's branch in South Asia, launched last year in India.

"Our directives will be the law for you from today," the email says, according to Bangladeshi news service bdnews24.com. "The consequences will be severe if you do not walk the path of Islam. Towering buildings will crumble to the ground, your heads will roll at the feet of the soldiers of Islam."