In the letter summarizing their claims, the women said they had faced retaliation since they were involved in the December protest. The workers said they had received difficult work assignments and improper warnings that could lead to firing. Amazon also had a “culture of surveillance after the protest,” Ms. Azmi said.

Muslim Advocates has withheld the women’s names from the public, saying they fear further retaliation. One of the women agreed to be interviewed on the condition of anonymity.

In the interview, the worker said that she had seen her manager looking at social media of the protests, and that he had then commented he noticed she had participated. Another time, a different manager took a photograph of her on his personal phone while she was working, she said, adding that when she complained, management played down her concerns.

According to the letter, one of the other women “has had her everyday conversations repeatedly video recorded by her supervisors.”

“There is zero tolerance for retaliation in the workplace,” Ms. Alfred, the Amazon spokeswoman, said. “We take any reports of retaliation seriously and look into all claims made by our employees.”

Amazon gives the workers paid breaks to pray up to 20 minutes, as required by state law, but the employees are still responsible for maintaining the same “rate,” or how many items they must pack in an hour. Ms. Alfred said workers could take longer prayer breaks without pay, for which productivity expectations would be adjusted.

Missing the rate can lead to write-ups and firing. The women said they and other Muslim workers feared taking time to pray, making it a “hostile environment” to be Muslim.