Unidentified assailants fatally stabbed two men in Bangladesh's capital Monday night, including a gay rights activist who also worked for the U.S. Agency for International Development, police said, in the latest in a series of attacks targeting atheists, moderates and foreigners.

Police said they suspected radical Islamists in the attack, which occurred two days after a university professor was hacked to death. There was no immediate claim of responsibility.

The victims were identified as USAID employee Xulhaz Mannan, who previously worked as a U.S. Embassy protocol officer, and his friend, Tanay Majumder, according to Mohammed Iqbal, a police officer in Dhaka's Kalabagan area. Mannan also was an editor of Bangladesh's first gay rights magazine, Roopbaan.

The U.S. ambassador condemned the murder, just weeks after the U.S. government and numerous rights groups called on the government of the Muslim-majority country to better protect its citizens and secure free speech.

"I am devastated by the brutal murder of Xulhaz Mannan and another young Bangladeshi this evening in Dhaka," U.S. Ambassador Marcia Bernicat said in a statement. "Xulhaz was more than a colleague to those of us fortunate to work with him at the U.S. Embassy. He was a dear friend."

According to a man who told local broadcaster Somoy TV that he had witnessed the attack, at least five young men took part in the killing and chanted "Allahu Akbar," or "Allah is Great" as they left the scene.

Bangladesh's government has blamed radical Islamists in the country, though the Islamic State group has claimed responsibility for some of the murders, including the killing Saturday of university professor Rezaul Karim Siddique in a northwestern city.

Government officials dismissed the claim, insisting that the extremist group has no presence in the South Asian country.

Bangladesh has been riven by a wave of deadly attacks on foreigners, religious minorities and secular bloggers, raising fears that religious extremists are gaining a foothold in the country, despite its traditions of secularism and tolerance.

The U.S. government has said it is considering granting refuge to a select number of secular bloggers facing imminent danger in Bangladesh.

"We abhor this senseless act of violence and urge the government of Bangladesh in the strongest terms to apprehend the criminals behind these murders," Bernicat said in her statement.