Former Secretary of State Hillary Clinton appeared to have a slight lead in Monday's Iowa caucus as her campaign issued a statement claiming victory, but Senator Bernie Sanders claimed a "virtual tie" in a razor thin vote.

The Iowa Democratic Party said in a statement the caucus was the closest in history, with some precincts reportedly having to resort to a rarely used rule to flip a coin to decide the winner. Clinton reportedly won all three of the coin tosses.

With 99 percent of the votes counted, Clinton hit 49.9 percent against Sanders' 49.6 percent. That amounts to Clinton being awarded 699.57 state delegate equivalents so far against Sanders' 695.49, while former Maryland Governor Martin O'Malley who dropped out of the race on Monday was awarded 7.68 state delegates and uncommitted were awarded 0.49 state delegates.

Under caucus rules requiring a 15-percent threshold, O'Malley and uncommitted votes must now be awarded to either Sanders or Clinton. And results from one precinct worth 2.28 state delegate equivalents are still not in.

With the results too close to call, the Iowa Democratic Party has refrained from calling a winner.

While Clinton said she was breathing a "big sigh of relief," her campaign has been surprised by the rise of the senator from Vermont ahead of next week's primary in New Hampshire, where Sanders enjoys a lead in the polls.

Clinton was looking to win Iowa after losing the key state in 2008 to President Barack Obama.

Sanders has organized youthful supporters in recent weeks, making significant ground in the polls against Clinton's formidable political machine.

As expected, Sanders gained support from younger voters, while Clinton did well among older voters. According to entrance poll interviews, 8 out of 10 caucus voters under the age of 30 said they supported Sanders, as did 6 out of 10 between 30 and 44.

However, in the 45 to 64 age bracket Clinton got nearly 6 out of 10 votes, while 7 out of 10 caucus-goers over 65 backed Clinton.

Sanders' comeback in Iowa has put to question whether or not Clinton's campaign could stumble going into key primaries over the next month.

A draw in Iowa and a win in New Hampshire, long considered a bellweather state, would give Sanders momentum going into Democratic primaries in Nevada and South Carolina later this month. Clinton is currently ahead in those states.

A key date to watch out for is Super Tuesday on March 1, in which 12 states are up for grabs.

Delegates for Clinton and Sanders will ultimately cast ballots at the Democratic National Convention in July.

cw/kms (AFP, AP, Reuters)