Fears Republican presidential nominee Donald Trump may be pursuing a Russian agenda with his candidacy have triggered a wave of alarm in the US.

A series of links between Trump's circle of advisers, his policy positions on the future of NATO, his statements of admiration for Russian president Vladimir Putin and even the overlap between his supporters and those touting pro-Russia views online have contributed to this view.

The concerns have prompted a series of high-profile American commentators and analysts to suggest Trump may be getting backing from Russia for his US campaign.

MIKE SEGAR/REUTERS U.S. Republican presidential nominee Donald Trump speaks at the Republican National Convention in Cleveland, Ohio, U.S. July 21, 2016. REUTERS/Mike Segar

Respected publications such as Slate, economist Paul Krugman writing in The New York Times, and The Washington Post have commented on the convergence between Trump's statements and geopolitical positions that Russia has long sought, with worrying implications should Trump become president.

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AARON P. BERNSTEIN US Republican presidential nominee Donald Trump takes the stage at the Republican National Convention in Cleveland, Ohio, US.

"Trump is making it clear that, as president, he would allow Russia to advance its hegemonic interests across Europe and the Middle East," wrote Jeffrey Goldberg in The Atlantic.

"His election would immediately trigger a wave of global instability."

Last week, Trump received the Republican nomination in a tumultuous and sometimes bizarre Republican Party Convention, after dominating his rivals in a primary season.

JIM YOUNG Donald Trump and his running mate Indiana Governor Mike Pence take the stage at the Republican National Convention.

Fairfax Media was among the first outlets to report on the overlap between Russian online support and the Trump campaign. The nature of the sometimes virulently anti-Semitic attacks on journalists who have written critically about Trump, the support of anonymous bloggers and voices, and even the use of confusion and violence at rallies match the kind of fear and intimidation tactics used in Eastern European campaigns.

However, online support is just one aspect where Russia is suspected in having a hand. Trump's campaign manager, Paul Manafort, has worked for Putin's Ukrainian ally, Viktor Yanukovych.

US Lieutenant-General Michael Flynn, who spoke for Trump at the Republican National Convention, appeared at an event with Vladimir Putin. Meanwhile, Trump's discussion of backing away from a key NATO guarantee has sent shudders through capitals around Europe.

AP Trump has expressed admiration for Russian President Vladimir Putin.

Trump's campaign even sought a change of language for US support for Ukraine, a country locked in a "frozen conflict" after Moscow annexed Crimea and began backing rebels in Ukraine's east.

More recently, the WikiLeaks release of Democratic Party data related to the Clinton campaign also suggests a Russian link.

Three independent groups verified that the hack of the information from the Democratic National Committee was committed by groups using techniques and identities with close links to Russia – despite denials of the alleged hacker, Guccifer 2.0.

DAVID BECKER/REUTERS The Clinton campaign has already said Russia hopes to affect the outcome of the election.

The information now being pumped out by WikiLeaks is clearly pitched to divide the Democratic Party before the Democratic Convention, beginning on Monday in the US (local time).

The Clinton campaign has already said Russia hopes to affect the outcome of the election.

"What appears evident is that the Russian groups responsible for the DNC hack are intent on attempting to influence the outcome of this election," the Clinton campaign said in June, when news of the hacking was revealed.

At the time, WikiLeaks had pledged to release information on the Democrats' campaign.

Originally created as a pro-transparency organisation, WikiLeaks has been seen in more recent years as friendly to Russia. The organisation routinely champions positions that adhere to Russia's geopolitical goals, and leader Julian Assange advocated Russia as a haven for Edward Snowden after the ex-US intelligence contractor fled the US in 2013.

In August of 2015, US counterintelligence expert John Schindler wrote that WikiLeaks is a "front for Russian intelligence".

Hillary Clinton, the former secretary of state, angered Russia with her support for the NATO alliance and her criticism of Russia's elections.