Washington  - Voting got underway Tuesday in primary elections in the states of North Carolina and Indiana in the battle between Hillary Clinton and Illinois Senator Barack Obama for the Democratic Party's presidential nomination.

Latest opinion surveys gave Obama a clear lead in North Carolina, but a close race between him and the former First Lady in Indiana.

The two states are the last of the largest ones remaining in the gruelling four-month-old primary election campaign. The initial returns are not expected before 2300 GMT.

Altogether 187 delegate votes - 115 in North Carolina and 72 in Indiana - are up for grabs in the two states.

Both campaigns played down expectations of landing a knock-out blow, as opinion polls suggested another split decision by voters in the two largest states left in the four-month-old nomination contest.

Obama, with his African-American background, has been expected to win North Carolina, a southern state which has a large African- American population.

In the mid-western state Indian, both sides are hoping to win over blue-collar workers that make up a large number of voters, a demographic group struggling amid an economic downturn in the United States that has typically favoured Clinton.

In the quest for the 2,024 delegates needed to capture the nomination at the Democratic Party national convention in late August in Denver, Obama currently leads by 1,743 to 1,606, according to a count by website realclearpolitics. com.

With just 200 delegates left in the six electoral contests remaining after Tuesday, both campaigns have turned to persuading nearly 300 undecided super-delegates - Democratic Party leaders and activists - who could still potentially swing the nomination in either candidate's favour.

The winner would face Arizona Senator John McCain, who has long since wrapped up the Republican Party's presidential race, in the national elections next November. (dpa)