Justice Antonin Scalia, a towering conservative voice on the US Supreme Court, has died at the age of 79, setting up a political showdown over his succession in the run-up to the presidential election.
His death, after three decades on the Supreme Court bench, comes 11 months before a new American president takes office, and could potentially tip the balance of the highest court in the land from its current 5-4 conservative majority to a liberal one.
The flag outside the Supreme Court was lowered to half-mast in tribute to Justice Scalia, who died in his sleep at a private residence in the Big Bend area of West Texas, according to the US Marshals Service.
President Barack Obama led tributes for the court's longest-serving justice, who was first appointed in 1986 by former president Ronald Reagan.
Who was Antonin Scalia?
- Served on the US Supreme Court for nearly 30 years
- Known for his strident conservative views and theatrical flair in the courtroom
- First Italian-American on the court and a devout Roman Catholic with nine children.
- Leader of the "originalist" ideology that interprets US Constitution based on its 18th century intentions
- An avid hunter who wrote the court's 2008 landmark opinion supporting gun rights
"For almost 30 years, Justice Antonin Scalia was a larger than life presence on the bench, a brilliant legal mind with an energetic style," Mr Obama said.
"We honour his extraordinary service to our nation and remember one of the towering legal figures of our time."
Mr Obama also made it clear he fully intended to nominate a successor to Justice Scalia, in accordance with his "constitutional responsibilities", after leading Republicans demanded the task be left to the next president.
He called for the Republican-controlled Senate to give his nominee a "fair hearing and a timely vote".
"These are responsibilities that I take seriously, as should everyone," Mr Obama said.
"They're bigger than any one party. They are about our democracy."
Chief Justice John Roberts mourned Scalia's passing as a "great loss to the court and to the country he so loyally served".
The president nominates a Supreme Court candidate, who requires Senate approval before taking up the lifetime post.
Republicans demand delay to nomination of Scalia's replacement
Conservative politicians immediately drew battles lines over the implications of the vacancy.
Republican Senate Majority Leader Mitch McConnell said Mr Obama should let the next president nominate the next Supreme Court judge.
"The American people should have a voice in the selection of their next Supreme Court Justice," he said.
"Therefore, this vacancy should not be filled until we have a new president."
US Senator and Republican presidential candidate Ted Cruz called for the 2016 to be "a referendum on the Supreme Court".
But leaving the nomination to the next head of state, who will not be sworn until January 2017, would mean the court is short-handed for a year or more.
Senator Chuck Grassley, the Republican chairman of the Senate Judiciary Committee, also issued a statement calling for a delay in the nomination.
"It's been standard practice over the last 80 years to not confirm Supreme Court nominees during a presidential election year," he said.
Mr McConnell's Democratic counterpart Harry Reid pressed for Mr Obama to send a nominee to the Senate "right away", stressing that a year-long vacancy would be "unprecedented".
"Failing to fill this vacancy would be a shameful abdication of one of the Senate's most essential Constitutional responsibilities," Mr Reid said.
The White House said Mr Obama would not rush the decision, but would wait until the US Senate is back in session next week.
The death of Justice Scalia, which former senior Obama adviser David Axelrod described as a "seismic event" that would have major impact on the presidential race, prompted White House hopefuls to quickly make their stance on succession clear.