The US Supreme Court has ruled that all states can demand photo identification papers from voters in a decision which could impact on the US presidential race six months before the elections.

By six votes to three, the judges upheld an appeals court decision backing a controversial Indiana law demanding voters provide proper picture identification such as a passport or driving licence before voting.

The ruling, which said demanding identification did not violate people's constitutional rights, could lead to many people being turned away at the ballot box.

In Indiana, some 43,000 residents of voting age, mainly elderly people, have neither a passport nor a driving licence.