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Barack Obama will become America's first black president after emerging triumphant from one of the most extraordinary US presidential elections in modern times.

There were tumultuous scenes among a crowd of 70,000 people at Grant Park in Chicago as early election projections showed him winning in key battlegrounds.

Although millions of votes were still to be counted, TV networks had already declared him the winner in Ohio and New Mexico - as well as holding Pennsylvania which John McCain knew he must wrest from the Democrats.

Mr McCain’s loss in Pennsylvania, along with another defeat in New Hampshire, left him with a pencil-thin path to the White House which relied on holding all the states won by President Bush four years ago. But Mr Obama's projected victories in Ohio and New Mexico should be enough to give him the 270 Electoral College votes he needs to become president.

A clutch of other once solid Republican states including Virginia, Florida, North Carolina and Nevada were said to be too close to call.

Turnout in the election was expected to be immense with the queues forming outside polling stations at dawn testament to the energy, excitement and expectations generated by Mr Obama through a campaign lasting almost two years.

Some of those waiting patiently in long lines were filled with hope, others with fear, still more with a sense of America at a crossroads, where Mr Obama will face economic convulsions at home and crises abroad.

The Democrat performed especially strongly among voters who regard the economy as the most important issue, cutting a swath through traditional battleground states in the east, while making deep incursions in Republican territory in the Mountain West and the South.

The campaign has long since been pregnant with historic possibilities, Mr Obama, bidding to become America’s first black president, first saw off a ferocious effort by Hillary Clinton to break the glass ceiling that has kept women from winning the White House. Then pushed John McCain, who had also breached his party's precedent by picking a female running mate in Sarah Palin, to the brink of defeat.

Wall Street rallied with US stocks rising faster than on any election day for 24 years in anticipation of the Treasury bailing out more stricken financial companies and an end to the uncertainty of the presidential campaign.

Mr McCain, before addressing his supporters outside a hotel in Phoenix, Arizona, struck a wistful note as he discussed his campaign."I've loved every minute of it," he said. "Every day, being able to meet the people we've met and go the places we've gone, it's been an unforgettable experience."

In the fight for Congress, Republicans suffered huge losses, but were clinging to hopes that they might just stop Democrats from reaching a filibuster-proof 60-seat "supermajority" in the US Senate.

Democrats, needing nine seats to reach the 60-seat threshold, were on target to gain at least seven, but narrowly failed to pick off Mitch McConnell, the Republican leader in the upper chamber.

In the House of Representatives, Democrats were on course to gain at least another 25 seats, giving them their biggest majority in the lower chamber for a generation.

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