The Republican candidate had been lagging behind, but may have crept ahead of the Democratic nominee in the last week, the surveys suggested.
However, forecasters say Mr Trump's lead was still within the polls’ error margins and experts emphasised it was too soon to call the election outcome.
Survey data released by American polling company Rasmussen Reports showed the lead Ms Clinton had enjoyed for most of the contest had disappeared, and put her behind Mr Trump for the first time since mid-July.
The latest weekly White House Watch report by the group, which targets likely voters by telephone and online survey, showed Mr Trump to have the support of 40 per cent of the US electorate, versus 39 per cent who said they supported Ms Clinton. The results are very different to the previous week's report, which put Ms Clinton at 42% and Mr Trump at 38%.
On Friday, Reuters reported the Republican candidate had pulled into a tie with his Democratic rival, based on their latest national tracking poll, produced in collaboration with Ipsos.
The poll showed the same results as the Rasmussen Reports data for the week beginning 26 August.
The news agency reported that Mr Trump has erased a substantial deficit and consolidated support among his party's likely voters in recent weeks.
Mr Trump's support among Republican voters increased six percentage points in the past fortnight, Reuters/Ipsos found, to about 78 per cent.
Meanwhile Ms Clinton has faced renewed criticism over her handling of classified information while serving as US secretary of state, and her family's charitable foundation has come under intense scrutiny over donations it accepted.
Polling aggregators, which calculate averages of major polls, have shown that Ms Clinton’s lead has been shrinking for the past few weeks. But in contradiction to the two new surveys, those averages still put her ahead of Mr Trump by between three and six percentage points.
Larry Sabato, director of the University of Virginia Center for Politics, said he remained convinced Ms Clinton was ahead.
“There has been a closing that’s completely natural,” Mr Sabato said.
“Every four years, you have two national party conventions that produce a bounce of varying sizes. Clinton got a substantial bounce this year that lasted for a full month. It’s usually gone around Labor Day, and by then we’ll be where we should be, which is right around four to five points [lead for Ms Clinton]”
Mr Trump has performed better this year in online or automated polls than in ones conducted by people.
Commentators say this could be because of 'shy' Trump voters who are ashamed to say they support the controversial candidate, but will turn out to vote for him on the day.
"We think there's a big hidden Trump vote in this country," campaign manager Kellyanne Conway told NBC last week.
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