Mitt Romney wins in Republican primary in Illinois.

Mitt Romney has won the Republican primary in Illinois, his latest win on the road to decide who will contest November's poll against Barack Obama, BBC News reported.

Romney has won 47% of the votes, compared with 35% for Rick Santorum, with 75% of votes counted.

Ron Paul polled 9% in Illinois and Newt Gingrich was on 8%; neither candidate campaigned extensively in the state.

"I'm running for president because I have the experience and the vision to get us out of this mess," said Romney, as his victory became evident.

Illinois sends 54 delegates to the Republican convention, and Romney hopes to maintain his momentum.

However, Illinois's delegates are not determined by the statewide vote.

Individual delegates are listed on the ballot in each of the state's 18 congressional districts and are identified by the candidate they support.

Santorum's campaign did not successfully file for the primary ballot in parts of Illinois, meaning he automatically cedes of those 10 delegates.

However, adressing supporters on Tuesday evening, Santorum said he had polled well in Illinois in areas "that conservatives and Republicans populate".

"We're very happy about that and we're happy about the delegates we're going to get, too," he said.

The candidates had clashed in Illinois over the economy.

On Monday Santorum had said he "didn't care about the unemployment rate", and told supporters the presidential campaign was about smaller government and winning back individual and social freedom.

Mr Romney jumped on those remarks later in the day, telling students in Peoria, Illinois "one of the people who is running also for the Republican nomination today said that he doesn't care about the unemployment rate".

"It does bother me. I want to get people back to work," Mr Romney said.

Later Santorum told supporters: "The economy is a big issue. Unemployment is a big issue."

Romney's victory in Illinois reportedly means that the gruelling Republican marathon goes on, the candidates straining on towards a finishing line that seems to recede further into the distance with every week that passes.