The reek of rhetorical gunpowder hung over Washington last night as Mitt Romney and President Barack Obama abruptly hurled themselves into the 2012 battle for the White House regardless of the lingering presence of other rivals for the Republican Party nomination.

War of words as challenger cruises to victory in Wisconsin, Maryland and Washington DC

Mitt Romney tightened his grip on the Republican presidential nomination last night, sweeping primaries in Wisconsin, Maryland and Washington DC, and shifted his focus to the general election with a sharp attack on President Barack Obama.

A Kansas man has revealed that hours after buying three tickets in last week's Mega Millions lottery frenzy that swept America, he was hit by lightning, proving the adage about how hopelessly small the chances are of winning.

America was a nation plunged into disappointment yesterday as all but three citizens realised their raids on the penny jar to buy tickets in a lottery with a jackpot of $656m (£409m) had come to nought.

Maryland state lottery officials announced early Saturday their state sold what could become the world's largestlottery payout of all-time, but it wasn't immediately clear if that ticket holder would get sole possession of the $640m (£400m) jackpot or have to split it with other winners.

An inmate at Guantanamo Bay has admitted helping al-Qa'ida plot attacks from his native Pakistan, in the first plea deal by one of the so-called "high value" detainees at the US base in Cuba.

New archaeological evidence suggests that America was first discovered by Stone Age people from Europe – 10,000 years before the Siberian-originating ancestors of the American Indians set foot in the New World.

A charity co-founder who claimed he travelled the world as a "Jewish Indiana Jones" to rescue Torahs has pleaded guilty to fraud charges, admitting that he lied about his exploits.

World Boxing Association vice president Gilberto Jesus Mendoza has confirmed they have granted Amir Khan a rematch against Lamont Peterson.

Bradley Manning's lawyers made their closing statements yesterday, in the preliminary hearing for the Army intelligence analyst accused of creating the biggest national security leak in US history.

Heather Watson's hopes of a third WTA quarter-final of the year ended with a three-set defeat by Canada's Stéphanie Dubois at the Citi Open in Maryland on Thursday.

Governments must start to vaccinate children and young adults against a strain of the influenza virus that killed several million people in the 1960s, a leading expert has warned.