The U.S. federal government is to resume executing death-row inmates after a 16-year hiatus, the justice department has announced.

Attorney General William Barr said in a statement he had directed the Bureau of Prisons (BOP) to schedule the executions of five inmates.

Barr said the five had been convicted of murders or rapes of children or the elderly.

The executions have been scheduled for December 2019 and January 2020.

"Under administrations of both parties, the Department of Justice has sought the death penalty against the worst criminals," Barr said in a statement. "The Justice Department upholds the rule of law - and we owe it to the victims and their families to carry forward the sentence imposed by our justice system."

Barr's announcement lifts what was an informal moratorium on the federal death penalty - as opposed to state-directed executions - since the 2003 execution of Louis Jones Jr, a 53-year-old a Gulf War veteran who murdered 19-year-old soldier Tracie Joy McBride.

Robert Dunham from the Death Penalty Information Center said the decision did not come as a surprise.

"President Trump has been a staunch supporter of capital punishment and has proposed several extreme uses of it, including for selling drugs and for all murders involving state and local police officers," he said.

"So it was not a surprise that he would seek to have executions carried out. I think the biggest surprise is that it took as long as it did."