Three police officers were shot to death and several others wounded in Baton Rouge, Louisiana on Sunday, the city’s mayor said, as the country remained on edge in the wake of police shootings of black men and the killings of five Dallas officers.

The officers in Baton Rouge were responding to a call of shots fired when they were ambushed by at least one gunman, Mayor Kip Holden told NBC News.

One suspect is dead and police are checking the shooting scene with a robot to make sure there are no explosives, Baton Rouge Police spokesman L’Jean Mckneely said.

Police told reporters authorities are seeking more than one suspect and said the public should be on the lookout for people dressed in black and carrying long guns.

Earlier, a spokesman for the East Baton Rouge Sheriff’s Office said police and sheriff’s deputies were involved in the shooting incident, which occurred around 9 a.m. local time (1400 GMT).

“Multiple officers from both agencies sustained injuries and were transported to local hospitals,” he said in an email. He said there were no firm numbers on the number hurt or the extent of injuries.

While the scene of the shootings was contained, police warned residents to stay away from the area, near Airline Highway, which is a mile from the Baton Rouge Police Department headquarters, where dozens of protesters were arrested earlier this month.

Two nearby hospitals were on lockdown, CBS reported. Efforts to confirm the report were not immediately successful.

It was not immediately clear whether there is a link between Sunday’s shootings and the recent unrest over police killings of black men in Baton Rouge and Minnesota.

A wave of protests against police violence in Baton Rouge and other cities erupted after Alton Sterling, a 37-year-old African-American father of five, was shot and killed at close quarters by law enforcement officers on July 5.

At a rally in Dallas to protest Sterling’s killing and a similar incident in Minnesota, a gunman opened fire on white officers, killing five of them.

The Black Lives Matter civil rights movement has called for police to end racial profiling, bringing the issue to national attention ahead of the Nov. 8 U.S. presidential election.

The Justice Department, which has opened a federal probe into Sterling’s death, declined to comment on Sunday’s shootings.

A White House official said President Barack Obama has been briefed on the shooting of police officers in Baton Rouge and will be updated throughout the day. The official added that the White House has also been in contact with local officials and has offered assistance.