Police said on Tuesday they were investigating an email sent to various media outlets reportedly by a banned militant 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. It urges businesses to fire any female employees, and says that working outside of the home is a "punishable offense" according to Islamic law. It does not elaborate what would constitute appropriate punishment. The letter is signed by the group Ansarullah Bangla Team, which is allegedly linked with several groups that claimed responsibility for killing four atheist bloggers this year. It threatens to kill more atheist bloggers, naming nine people living abroad and six living in Bangladesh, and warns their backers that "no one will be spared if you support atheists." The email, received Monday by many Bangladeshi media outlets but not the Associated Press, says those living abroad would be targeted as soon as they returned to Bangladesh. It said the list of 15 names was not final and that anyone who attempts to degrade Islam would face serious consequences. Authorities said they were taking the threat seriously and were investigating. "Higher authorities have been informed," Dhaka police spokesman Muntasirul Islam said on Tuesday. The email has renewed concerns about radical forces within Bangladesh. Since late September, two foreigners — an Italian aid worker and a Japanese agricultural worker — have been 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 online news service bdnews24.com and the Dhaka Tribune newspaper. Ansarullah also allegedly has ties with Al-Qadeda'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." It warns the media, "If your freedom of expression breaks the limit we have set, every news media unit should be prepared to face (the consequences) of our freedom to vent our anger," according to bdnews24.com. It also says anyone working for a media company that publishes reports condemning the "jihadis" for attacks "will be considered to be abettors of atheists and atheism, and they would be fully uprooted."