A coalition including civil liberties and human rights activists urged US lawmakers Tuesday to reject a bill that would require Internet companies to report signs of "terrorist activity" on their networks.

More than 30 organizations endorsed an open letter urging the Senate to reject the measure included in an intelligence authorization act which cleared a committee and had been on track for Senate passage without debate.

"Turning Internet companies into informants for the government flies in the face of individuals' fundamental right to privacy," said Emma Llanso, at the Center for Democracy & Technology, one of the groups leading the opposition.

"People who know their online service providers are required to turn over a broad category of communications and 'activity' to the government will face a serious chilling effect on their willingness to access information and speak their minds online."

The groups said the Senate was set to consider passage by unanimous consent, or without debate, before Senator Ron Wyden objected, temporarily blocking the bill.

They noted that the reporting provision was added during closed proceedings of the Senate Select Committee on Intelligence and would require social media platforms, telecom providers, cloud services and websites to provide authorities with their users' personal information and communications content if terrorist activity was suspected.

"Unfortunately, this provision would create strong incentives for providers to overreport on the activity and communications of their users in order to avoid violating the law," the letter said.

"This provision risks bringing wholly innocent people under the scrutiny of the US government in a procedure that includes no limits on the use of the reported information and no safeguards against abuse."

Signatories of the letter include the American Civil Liberties Union, Human Rights Watch, Consumer Federation of America and the Software & Information Industry Association.

Wyden, in blocking the bill, said it had "a flawed provision that would require companies like Twitter and Facebook to make judgments about when users' speech constitutes 'terrorist activity.'"

Markham Erickson of the law firm Steptoe and Johnson said in a blog post that the provision could "serve as a global template for other countries to impose reporting requirements for activities those jurisdictions deem unlawful."