Latest updates: Follow our full coverage on the US election
Republicans are set to control the US Senate for the first time in four years after capturing target seats from Democrats, securing a conservative sway over the next president's cabinet.
Wins for Republican candidates in previously Democratic-held seats in Ohio and West Virginia mean Donald Trump's party will have at least 51 out of 100 seats in the Senate. Uphill Democratic battles to fight back with gains in Texas, Florida or Nebraska fell short as results poured in.
Republicans were hunting further gains in Democratic-held states including Montana, Michigan and Pennsylvania, where races were too close to call. The battle to control the the House of Representatives, won by Republicans in 2022, was not yet decided.
The results give Republicans an important power centre in Washington and a role in confirming the next cabinet, as well as any Supreme Court vacancies that arise under the next president. The Senate was twice asked to vote on impeachment charges during Mr Trump's first term in the White House.
Bernie Moreno, the Republican winner in Ohio, is a Trump-backed, Colombian-born businessman who will be the first Latino to represent the state in the Senate. He defeated Democratic incumbent Sherrod Brown after candidates spent $500 million on one of the most expensive Senate contests in history.
“We talked about wanting a red wave. I think what we have tonight is a red, white and blue wave,” Mr Moreno said in a speech praising Mr Trump and pledging to help advance his agenda if Republicans win the White House.
West Virginia's Republican Governor Jim Justice, who defected from the Democrats at a Trump rally in 2017, gained the Senate seat previously held by Joe Manchin, who had been an outlier as a conservative Democrat in an increasingly Republican-leaning state.
The Republican candidate in Pennsylvania is Dave McCormick, a George W Bush administration official whose Egyptian-American wife Dina Powell is a former deputy national security adviser to Mr Trump. He is seeking to unseat Democrat Bob Casey for another Republican gain.
Nebraska Republican Deb Fischer won the landmark 51st seat in an unexpectedly close race against military veteran Dan Osborn, who gained traction during the race by rejecting both major political parties to run as an independent. Ted Cruz won re-election in Texas to hold another Republican seat.
“Tonight the people of Texas have spoken, and their message rings clear as a bell across our great state: Texas will remain Texas,” Mr Cruz said to cheers from supporters, many of whom held signs that read: “Keep Texas Texas.”
The new Senate will also include New Jersey Democrat Andy Kim, a former adviser on Iraq to the Obama administration who will become the first Korean-American in the chamber. Democrats held the seat despite Mr Kim's predecessor Bob Menendez being found guilty of bribery and resigning in July.
An internal power struggle is on the cards to steer the Republican Senate majority after long-time leader Mitch McConnell announced his intention to step down. One contender, John Cornyn, said he looked forward to "working with our new conservative majority to make America great again".
A second, John Thune, said the party could "turn the page on this expensive and reckless chapter of American history". Republican Senators have already been looking at ways to extend tax cuts that were passed during Mr Trump’s term, as well as sending funding towards toughened border security measures.
