Dallas police officers enter Dallas Police Department headquarters after the all-clear signal was given due to a lockdown after an anonymous threat was reported in Dallas, Texas, US July 9, 2016. [Photo/Agencies]

DALLAS - Police in the US city of Dallas, Texas, stepped up security Saturday after a new threat was received, two days after snipers killed five police officers during a mass protest in the city.

Dallas police confirmed that it received an anonymous threat against the law enforcement across the city and said that the department was taking precautionary measures to heighten security. The police did not reveal details of the threat.

A Special Weapons and Tactics (SWAT) unit was deployed around the Police Department's headquarters on South Lamar Street into Saturday night, including on roofs and in armored vehicles.

Roads leading to the police headquarters were blocked late Saturday. An armed black policeman at the crossroads between Belleview Street and Akard Street said he has received orders to block the street, but declined to disclose more information.

Sources said the Dallas police were searching for a suspicious man who might be hiding in the police headquarters' garage.

Later reports by the police said that they conducted multiple searches of the parking garage, including with a canine unit. The SWAT team detonated a device to break through a locked fence inside the garage.

The police declared everything clear later in the night.

On Thursday night, snipers hiding in a multi-story garage opened fire on police officers during a mass protest in downtown Dallas against recent killings of African-Americans by police officers. The snipers reportedly targeted white people, killing five officers and injuring seven others. One of the suspects, a veteran, was later killed by a police bomb robot after a stand-off of several hours.