Cyberattacks coming from Russia, China and Iran have been targeting the upcoming presidential election in America, according to Microsoft.

In a statement published today, Microsoft said the activity made it clear that "foreign activity groups have stepped up their efforts targeting the 2020 election".

However, the company has said that the majority of the attacks were "detected and stopped" by security tools within their products, and those targeted had been notified.

READ MORE: Boris Johnson's top official admits 'integrity of the union' in doubt

Microsoft has observed hacking activity from Strontium, operating from Russia with attacks on more that 200 organisations including political campaigns, advocacy groups, parties and political consultants.

According to the company, the same Russian military intelligence outfit that hacked the Democrats in 2016 has been attempting similar intrusions, which appears to be part of a broader increase in targeting of US political campaigns and related groups.

"What we've seen is consistent with previous attack patterns that not only target candidates and campaign staffers but also those who they consult on key issues," Tom Burt, a Microsoft vice president, said in a blog post.

Similarly, Chinese operation Zirconium has reportedly attacked high-profile individuals associated with the election - in particular those associated with Joe Biden.

Meanwhile, Phosphorus - operating from Iran - had been attacking the personal accounts of those associated with Donald Trump's campaign. 

The company would not comment on who may have been successfully hacked or the impact, and Microsoft did not assess which foreign adversary poses the greater threat to the integrity of the November presidential election.

However, the consensus among cybersecurity experts is that Russian interference is the gravest.

READ MORE: BBC Scotland stopping daily live coverage of Nicola Sturgeon's coronavirus briefings

Senior Trump administration officials have disputed that, though without offering any evidence.

"This is the actor from 2016, potentially conducting business as usual," said John Hultquist, director of intelligence analysis at the top cybersecurity firm FireEye.

"We believe that Russian military intelligence continues to pose the greatest threat to the democratic process."

The Microsoft post shows that Russian military intelligence continues to pursue election-related targets undeterred by US indictments, sanctions and other countermeasures, Mr Hultquist said.

It interfered in the 2016 campaign seeking to benefit the Trump campaign by hacking the Democratic National Committee and emails of John Podesta, the campaign manager of Hillary Clinton, and dumping embarrassing material online, congressional and FBI investigators have found.

The same GRU military intelligence unit, known as Fancy Bear, that Microsoft identifies as being behind the current election-related activity also broke into voter registration databases in at least three states in 2016, though there is no evidence it tried to interfere with voting.

US intelligence officials said last month that the Russians favour President Donald Trump and the Chinese prefer former vice president Joe Biden, the Democratic challenger.

Evidence shows that China is largely an espionage threat, while Russia steals data and weaponises it.