The US embassy asked its citizens to take precautions.
In a rare security alert, the US embassy in Tanzania has told its citizens to take precautions over rumours of impending attacks in a tourist area of the main city Dar es Salaam.
"There are rumours of impending attacks in the Masaki area of Dar es Salaam, specifically at hotels and restaurants frequented by tourists, and at Slipway Shopping Centre on the Msasani Peninsula," the embassy warns.
However it also says it "has no substantiating evidence of the threat or information on the timing".
Responding to the warning, Inspector of General of Police Simon Sirro said he was aware of the rumours and the police are following them up.
"It's news like any other news, it might be true or false, but we don't ignore it," he told BBC Swahili.
He added that the intelligence service had the information since Tuesday.
In 1998, the US embassy in Dar es Salaam was targeted in an al-Qaeda bombing in which 11 people died.
But there have been no attacks on foreigners in Tanzania since then.