The US has put its diplomats in Saudi Arabia on a raised state of alert due to security concerns there.
Foreign workers' compounds are a clear target for militants in Saudi Arabia
A statement from the US embassy in Riyadh said it had restricted diplomats in visiting the city's housing compounds, where many Westerners live.
Last month 18 people died when suicide bombers targeted a foreign workers' compound in the city.
Shortly after the new US warning, Saudi authorities named 26 suspects wanted in connection with attacks in the kingdom.
The US embassy said there was evidence at least one such compound was under active surveillance by "terrorists", the statement said.
It said the Seder Village compound in Riyadh was being monitored and added there was "credible information" others across the country were also being watched.
The US said its citizens should remain vigilant
Diplomats and their dependents should only visit the compounds on official business and only during the day, it said.
It is the second time the embassy has warned that the Seder Village compound could be a target.
The statement also urged US citizens visiting or living in Saudi Arabia to register with the embassy or US consulates across the country and encourages them to remain vigilant.
Hours before November's attack, the US shut all its diplomatic missions in the country having received intelligence of a terror threat.
Meanwhile Saudi officials on Saturday released the names of 26 suspects wanted in connection with attacks and said a $1.9m reward would be paid to anyone who thwarted a militant attack.
Lesser rewards are promised for information leading to the arrest of a militant suspect or group.
Most of the suspects are Saudi nationals although two are thought to be Moroccan and one Yemeni, Reuters news agency reported.
The warning to US diplomats also comes only days after the UK Foreign Office renewed its warning to avoid non-essential travel to the kingdom following the discovery of a terror plot.
Saudi Arabian officials foiled a bomb attack in late November when they discovered a car packed with more than a ton of explosives. Two suspected militants were also killed in a shoot-out with police following the discovery.
US and Saudi Arabian authorities blamed November's bombing on Osama Bin Laden's al-Qaeda network.
In May this year at least 34 people, including nine suspected suicide bombers, died when a series of co-ordinated truck bombs exploded in foreign workers' compounds across Riyadh.