DHAKA, Bangladesh — Fear has wormed its way into the mind of Mithila Farzana, who hosts two talk shows on a Bangladeshi television news channel.

These days, she is so alert to the sensation of men coming up behind her that when she walks the halls of the university in Dhaka where she teaches, she will step aside, heart racing, to let students pass. Her husband will no longer allow her to take a car service to work, reasoning that in a city that is home to well-resourced radical networks, “a driver can sell himself easily,” she says. He drives her himself.

In the past, Ms. Farzana could survey the danger from a professional distance, reporting the facts each time militants murdered one of the bloggers campaigning against fundamentalist Islam.

Then, last month, a shadowy group — the one that claimed responsibility for killing the bloggers — sent a letter to a television news channel warning that unless news media stopped employing unveiled women as journalists, “the outcome will be dreadful.” On Saturday, militants carried out simultaneous attacks on two book publishers — not secular activists, this time, but low-profile businessmen who acted as intellectual supply lines for some of the country’s most prominent writers.