Following last week's terrorist attack on the Canadian parliament, security measures are being ramped up by the Department of Homeland Security at an undisclosed number of government buildings in Washington and other major U.S. cities due to continuing terror threats, Homeland Security Secretary Jeh Johnson said on Tuesday.

Citing the enhanced security to only be a "precautionary step" at "various U.S. Government buildings in Washington DC and other major cities and locations around the country," Johnson said there had been no credible information about any specific threat against a U.S. target, according to Reuters.

"Given world events, prudence dictates a heightened vigilance in the protection of U.S. government installations and our personnel," he said.

However, supporters of terrorist organizations, including the Islamic State and al-Qaeda, have repeatedly called on "lone wolves," through the use of social media, to execute attacks on the United States, a U.S. official, who spoke on condition of anonymity, said, adding that a stream of threats from militant groups which U.S. agencies have been monitoring for months had brought on the new measures.

"The reasons for this action are self-evident: the continued public calls by terrorist organizations for attacks on the homeland and elsewhere, including against law enforcement and other government officials, and the acts of violence targeted at government personnel and installations in Canada and elsewhere recently," Johnson said in a statement.

He also warned U.S. state and local officials responsible for security to be on their guard especially for possible "small-scale attacks by a lone offender or a small group of individuals."

The Federal Protective Service, a division of DHS, is allotted an annual budget of more than $1.3 billion, which is paid as security fees by the agencies it protects, to provide security for more than 9,500 federal offices and courthouses throughout the country, including Capitol Hill, Supreme Court, park or military installation, according to USA Today.

At this point, it is unclear how much the additional security measures will cost and the information remains "law-enforcement sensitive," Johnson said, declining to offer more details.

Meanwhile, Rep. Michael McCaul, R-Tex., the chairman of the House Homeland Security Committee, pointed to recent efforts by the Islamic State to recruit homegrown terrorists in the United States via social media. "We must do everything we can to protect every American abroad and at home," he said in a statement.