Image copyright EPA / AFP Image caption Mrs Clinton and Mr Trump rolled out duelling lines of attack this week

US presidential hopefuls Hillary Clinton and Donald Trump have sharpened their attacks as they both turn their attention to the general election.

Mrs Clinton targeted Mr Trump's business record, noting firms run by the New York businessman have filed for bankruptcy protection four times.

"How could anybody lose money running a casino?" Mrs Clinton asked on Monday.

Mr Trump released an advert on Monday re-airing sexual assault allegations against Mrs Clinton's husband.

The advert featured two women - Kathleen Willey and Juanita Broaddrick - who have accused former President Bill Clinton of sexually assaulting them years ago.

The video includes footage of Mr Clinton with a cigar in a mouth and Mrs Clinton laughing.

It ends with the tagline: "Is Hillary really protecting women?"

Mr Clinton has repeatedly denied that he assaulted the women, and he was never criminally charged as a result of the accusations.

Analysis: Anthony Zurcher, BBC North America reporter

Image copyright Instagram Image caption Mr Trump's advert focused on past accusations against Mr Clinton

Hillary Clinton and Donald Trump have given us a window into the future of the 2016 general election campaign, and it looks like it will be all about the past.

Mr Trump seems intent on rehashing the political battles of the 1990s and Bill Clinton's uneven legacy - perhaps to tarnish Mrs Clinton directly or just to emphasise exactly how long she's been on the political scene. Mrs Clinton is diving into Mr Trump's lengthy, and relatively unexploited, track record of questionable business dealings and inflammatory statements.

The two candidates already have record-setting negative ratings, and if this is the shape of things to come it seems highly unlikely either White House hopeful will be able to improve their image.

Get ready for five months of mud-slinging, alarm-sounding and umbrage-taking. The least reviled candidate left standing can claim the prize - but may be in no position to do much with it.

Mr Trump and his supporters have charged that Mrs Clinton tried to discredit her husbands' accusers.

The businessman has signalled his campaign will bring scandals from the Clinton administration into the 2016 race.

On Monday, Mr Trump said he thought the death of White House aide and Clinton friend Vince Foster was "very fishy".

Law enforcement officials and a subsequent federal investigation ruled that Foster killed himself in 1993, but conspiracy theorists have long tried to connect the Clintons to his death.

Image copyright Getty Images Image caption Mr Trump sold off his casinos after the resorts underwent years of financial problems

Mrs Clinton has declined to directly address Mr Trump's accusations, instead focusing on Mr Trump's business record and his past statements about women.

In 1991, the Trump-owned Taj Mahal filed for bankruptcy and the Trump Castle Associates followed suit in 1992.

The Trump Hotel & Casino Resorts filed bankruptcy for in 2004 while the Trump Entertainment Resorts sought Chapter 11 protections in 2009. Mr Trump has since left the casino business.

"Trump economics is a recipe for lower wages, fewer jobs and more debt. He could bankrupt America like he has bankrupted his companies," Mrs Clinton said.