Washington, Mar 26 (DPA): The US Congress Thursday approved one last round of changes to the landmark health reform bill already signed into law by President Barack Obama, ending a divisive year-long domestic debate that has taken a violent turn this week.

The votes in the Senate and House of Representatives marked the final steps in a complicated set of procedural manoeuvres that have played out in a bid to get Obama's top domestic priority through the legislature. Republicans, united in opposition to the reforms, have used every available procedure to slow the process.

There were reports of scattered violence as opponents vandalized Democratic Party facilities and sent death threats to lawmakers who supported the health overhaul. Republicans said they, too, received threats and one said a bullet was fired into a window of his office.

Both political parties condemned the violence and appealed for calm Thursday, but simultaneously traded accusations of fuelling the protests with their passionate rhetoric.

The Senate voted 56-43 on a "reconciliation" bill that was first approved by the House of Representatives Sunday. The vote came after a marathon debating session that began Wednesday and ended A.M. Thursday. The chamber reconvened at 9:45 A.M. Thursday and took its final vote four hours later.

Yet Republicans had succeeded in finding two relatively minor provisions that had to be struck from the legislation, forcing the House to take one final vote on the package.

The House approved the changes for a second time late Thursday evening by a 220-207 vote, finally ending the protracted legislative debate that has dominated Obama's first year in office.

"We're all tired, but this has been a legislative fight that will be in the record books," said Harry Reid, the Senate's top Democrat.

Obama Tuesday already signed into law the dramatic overhaul of the country's health care system that aims to provide nearly all Americans with access to at least some form of health insurance. The president will give another signature in the coming days on the new set of changes.

Obama Thursday took his case on the road to convince a sceptical public of the need for reforms, which also impose new regulations on insurance companies and constitute the most comprehensive changes to the US health sector in four decades.

Republicans are hoping to capitalise on public anger against the reforms during mid-term congressional elections in November, vowing to repeal the legislation if they regain control of Congress.

Obama challenged conservatives to "go for it" during a townhall-style gathering in Iowa City, Iowa.

"If they want to have that fight, we can have it," Obama said. "Because I don't believe that the American people are going to put the insurance industry back in the driver's seat."

The White House also urged calm as the debate turned violent this week. Spokesman Robert Gibbs said "we ought to be able to have a debate that is done in a way that's civil without any threat of violence".

During protests over the weekend, some lawmakers faced racial slurs and other epithets as they entered Washington's Capitol building to take their final vote on the legislation.

Some Democrats accused Republican leaders of encouraging the attacks with their over-heated rhetoric against the health reforms. House Speaker Nancy Pelosi said it was important for members of Congress to "understand the impact of our words on others".

Those charges were sharply rejected by conservative leaders.