Law enforcement agencies in several major US cities have issued alerts advising residents to be vigilant in the wake of the US strike against Iran’s top general as officials said they were stepping up security efforts at sensitive locations.

Chad Wolf, acting secretary of the US Department of Homeland Security, said his agency was working with law enforcement officials and others across the country and was ready to respond to any threats, though none had yet been detected.

In New York City, Mayor Bill de Blasio announced he was consulting with city officials about steps the the police department will take to protect key locations “from any attempt by Iran or its terrorist allies to retaliate against America”.

The city will be “vigilant against this threat for a long time to come”, De Blasio tweeted

The New York police commissioner, Dermot Shea, added: “NYPD continues to closely monitor the events in Iran & across the region for any further developments. While there are no specific / credible threats to #NYC, we’ve deployed additional resources to key locations. As always, if you see something, say something.”

Los Angeles, home to a sizable US-Iranian population, also issued an alert hours after the US strike on Qassem Suleimani, asking “every Angeleno to say something if you see something”.

The communication was followed by a second Los Angeles police department (LAPD) message, posted on Twitter, that also emphasized there was no current threat.

“While there is no credible threat to Los Angeles, the LAPD is monitoring the events developing in Iran. We will continue to communicate with state, local, federal and international law enforcement partners regarding any significant intel that may develop.”

The warnings came as the US state department urged its US citizens to leave Iraq “immediately”.

The US embassy in Baghdad, which was attacked by Iran-backed militiamen and other protesters earlier this week, is closed and all consular services have been suspended.

The intervention of domestic law enforcement comes amid newly rising tension over foreign-backed terrorism.

In November, a “sleeper agent” of Hezbollah, the Iran-backed Lebanese group listed by US authorities as a foreign terrorist organization, was sentenced to 40 years in prison by a federal court over plans to conduct terrorist attacks around New York.

Prosecutors claimed that Ali Kourani was “recruited, trained and deployed by Hezbollah’s Islamic Jihad Organization” and had spent “years conducting surveillance on the city’s critical infrastructure, federal buildings, international airports, and even daycare centers”.

The FBI assistant director William F Sweeney Jr said Kourani’s arrest was “a reminder to us all that New York City and its surrounding areas remain primary targets for those looking to conduct a violent attack against our way of life”.