"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 the travel alert.
Anisuzzaman - known only by his surname and a professor of Bengali literature at the Dhaka University - told bdnews24.com that the death threat text message "asked in proper English why I support bloggers and if I wanted to die on being struck by machete".
Timeline: Attacks on bloggers and publishers
27 February: Avijit Roy attacked and killed while walking home from a book fair. His wife Bonya Ahmed was also hurt