Gun control activists rally in front of the White House in Washington, Jan 4, 2016. [Photo/Agencies]

Republicans vow to fight

Republican leaders were quick to denounce Obama's gun changes, with most Republican candidates for the 2016 presidential race promising to reverse his actions if they win the White House.

Democratic candidates praised the moves.

Reince Priebus, the head of the Republican National Committee, said the changes were "all about burnishing the president's legacy and boosting Democrat enthusiasm in a presidential election year."

Republicans who control Congress made it clear that they oppose the changes, although some downplayed their significance.

"Ultimately, this executive 'guidance' is only a weak gesture - a shell of what the president actually wants," said Kevin McCarthy, leader of the Republican majority in the House of Representatives.

Democrat Senator Joe Manchin of West Virginia appeared to be in a minority in his party in voicing opposition to Obama's actions.

"Instead of taking unilateral executive action, the US President should work with Congress and the American people, just as I've always done, to pass the proposals he announced today.

"Like all law-abiding Americans and gun owners, I want to prevent future incidents of gun violence and keep firearms out of the hands of criminals and the mentally ill, but legislation and consensus is the correct approach," Manchin said in a statement.