US Republican presidential candidate Ted Cruz speaks during a campaign event in Des Moines, Iowa January 31, 2015.[Photo/Agencies]

DES MOINES, Iowa - Republican Ted Cruz pulled ahead of Donald Trump while Democrat Hillary Clinton narrowly led rival Bernie Sanders on Monday in early results from Iowa's presidential nominating contest, the first in the 2016 race for the White House.

Cruz, a conservative US senator from Texas, led the billionaire businessman 27.9 percent to 24.5 percent in the Republican race with 76 percent of the precincts reporting results. Marco Rubio, a US senator from Florida, was in third place with 22.7 percent, making him easily the leader among establishment candidates.

Clinton, a former secretary of state, held a lead of 50.4 percent in the Democratic race compared to 49.0 percent for Sanders, a self-styled democratic socialist US senator from Vermont, with 79 percent of the precincts reporting.

Former Maryland Governor Martin O'Malley, who had trouble gaining any traction in the Democratic race, planned to suspend his campaign at 9:30 pm CST (0330 GMT), according to a Democrat with knowledge of his plans. O'Malley was in third place with 0.5 percent.

Republican voter turnout far exceeded the normal average from previous years. Long lines were reported at many caucus sites with many new voter registrations.

"They say the record crowds are good for us so we'll see what happens," Trump said, acknowledging he was "a little bit" nervous.

A Cruz win would upset momentum for Trump, who is leading in national polls for the Republican nomination.

"We can and we will get back to the founding principles that made America great," Cruz said on Twitter.