Republican contest: Rick Santorum 'wins' Louisiana poll

Rick Santorum has won the Republican presidential primary in the southern US state of Louisiana, US media project.

Partial results gave the former Pennsylvania senator 39%, well ahead of the front-runner Mitt Romney, who had 30%.

Mr Santorum is seeking to close the gap on the ex-Massachusetts governor to become the party's nominee to challenge Barack Obama's in November's election.

Mr Romney has so far won 21 out of 33 contests to Mr Santorum's 10.

Former House Speaker Newt Gingrich was trailing in Lousiana's poll in third place, ahead of Texan Ron Paul - who has yet to win a poll.

Mr Santorum enjoys strong support among conservatives in the south, and he has also picked up backing from Republicans who have peeled away from Mr Gingrich as he lost momentum.

However, Mr Romney is widely tipped to regain the advantage when the race moves on in April to Wisconsin, Maryland and Washington DC.

See detail of all states won

A candidate needs 1,144 delegates to win

He also received a boost earlier this week when he secured the endorsement of former Florida Governor Jeb Bush.

Mr Bush called on Republicans to "unite" behind the Romney campaign.

Correspondents say the backing of the respected Republican suggests the party establishment could be coalescing around Mr Romney.

In another boost, FreedomWorks, an organisation that supports the Tea Party movement, dropped its opposition to Mr Romney's candidacy.

Mr Romney has so far won 563 delegates and Mr Santorum's 263, according to an estimate by the Associated Press news agency.

A candidate needs to accumulate 1,144 delegates to the August convention in order to secure the nomination.