Foreigners may be attacked again in Bangladesh, the US State Department said in a travel alert on Tuesday that urged Americans to be cautious and vigilant in that country.

A Japanese citizen was shot dead in Bangladesh on October 3 and an Italian aid worker was killed in the same manner in the capital Dhaka on September 28 in attacks claimed by the Islamic State militant group.

"There is reliable information to suggest that terrorist attacks could occur against foreigners in Bangladesh, including against large gatherings of foreigners," the State Department said in a travel alert that cited the two killings as well as the October 24 bombing of a Sha religious procession.

"During 2015 there has been a series of threats and terrorist attacks targeting writers, publishers, and others in the media, including the murder of a US citizen blogger," it added. "The US government assesses that the terrorist threat remains real and credible, and further attacks are possible."

Attacks on foreigners are relatively rare in Bangladesh, despite a rising tide of Islamist violence over the past year that has seen four online critics of religious militancy hacked to death, among them a US citizen of Bangladeshi origin.

Asked about the fresh travel alerts, spokesperson of the US embassy in Dhaka told The Daily Star, "The Alert does not reflect a new threat. The Alert is intended to inform the public of the existing threat, given the increased numbers of foreigners expected to travel in the near future for large-scale public events."