David Cameron says he wants to bring the UK together, claiming the Conservatives appear to have achieved "a very strong night".
As the SNP continue to sweep Labour and the Lib Dems out of Scotland, the prime minister said he wanted to govern "one nation, one United Kingdom".
The BBC suggests Mr Cameron's Tory Party is on course to win 325 seats, enough for a Commons majority.
Employment minister Esther McVey is the biggest Tory loss so far.
But Ms McVey, who lost her Wirral West seat to Labour by 417 seats, went out fighting, adding: "I'm coming back - I want to be an MP."
However, the story of the night has been the party's success.
Speaking at the count in his Witney constituency, Mr Cameron said it was "too early to say exactly what sort of result" would emerge from the election.
But he said: "This is clearly a very strong night for the Conservative Party - I think we've had a positive response to a positive campaign...
"My main aim is simply to govern on the basis of governing for everyone in our United Kingdom."
Former Conservative leadership contender David Davis said was "a reasonable chance" the party would win the election outright.
"It depends exactly on the numbers - I think there's a reasonable chance that we'll actually get above 326 [the figure needed to command a majority]," he said.
Professor John Curtice, who led the exit poll operations, also suggested the Conservatives could achieve an overall majority.
He was speaking after Conservative Marcus Jones held on to the marginal seat of Nuneaton shortly before 02:00 BST.
The exit poll had expected a one point swing to Labour in that seat, when in practice there was a three point swing to the Tories.
By 06:00 BST, the Conservatives had gained 30 seats - and lost eight.
London Mayor Boris Johnson, who won the Uxbridge and Ruislip South seat with a 10,000-vote majority, said: "We're very excited by some of the results that are coming through. Overall, I think it's been an amazing night for the Conservatives."
But he said all parties must take account of the rise of the SNP in Scotland.
"There has to be some sort of federal offer'' in light of the huge increase in SNP MPs, he said.
Conservative Chief Whip Michael Gove described the exit poll figures as "an unprecedented vote of confidence in David Cameron".
'Considerable authority'
Mr Gove said if the exit poll was right, "it means the Conservatives have clearly won this election and Labour has clearly lost".
"We haven't had an incumbent government increase its majority like this since 1983.
"And it would be an unprecedented vote of confidence in David Cameron's leadership and in particular in the message that we have reinforced throughout this campaign, which is that if people wanted to secure our economic security, they've got to make sure that David is in Downing Street."
He said it was too early to talk about potential post-election deals but if the exit poll proved right, "tomorrow the prime minister will outline the basis on which we can go forward with a secure and stable government in the national interest".
Mr Cameron would enjoy "considerable authority", he said, and it would be "by any measure a success" for him.
The prime minister has previously suggested anything short of an overall majority would be a failure.
But Labour's shadow home secretary Yvette Cooper said she was "puzzled" by the exit poll and urged people to wait for the results before making predictions.
"It doesn't reflect any of the conversations and responses we've had," she said.
Home Secretary Theresa May said a high turnout among voters would suggest people were "captivated by this campaign and the importance of this general election".
'Price' to pay
If the Conservatives do enjoy the success predicted in the exit poll, they could look to the Liberal Democrats - forecast to win 10 seats - to provide some additional support.
DUP member Sammy Wilson said there would be "a price" to pay if his party entered any form of coalition with the Conservatives.
"The emphasis will be on getting the government at Westminster to recognise the economic difficulties we have in Northern Ireland," he told the BBC.
This would include looking at the impact terrorism has had on Northern Ireland's infrastructure and rebuilding the economy to make it less dependent on the public purse, he said.
Source: BBC
hizi exit polls ni changa la macho.
Ila kama ni kweli basi Conservatives wameua aisee.
Yaani ukijumlisha viti vya Labour, SNP, Liberal Democrats, na UKIP bado havifikii idadi ya viti vya Conservatives.
Wow...just wow.
Sasa tusubiri tuone kama kama hizi exit polls zinaakisi uhalisia.
tetetetetet naona ukip wamefanya yao. Paka sasa conservative hawaamini ukipi kupanfa kwa 19%labour washachukua kiti kimoja cha sunderland. ....lkn mi sio mpenzi wa hii style ya mwenye viti vingi ndio anaunda serikali na sio mwenye kura nyingi, maana kama sunderland mp wa labour kashinda kwa zaidi ya kura 21000 dhidi ya 7000 za conservative lkn hapo wakija kwenye kumpata waziri mkuu basi inahesabika kama ed kapata kura moja na cameroon hajapata kitu mpk sasa
tetetetetet naona ukip wamefanya yao. Paka sasa conservative hawaamini ukipi kupanfa kwa 19%
hivi vyama vyenye chuki za kutisha dhidi ya wahamiaji vinapata umaarufu mkubwa eu, si muda mrefu ujao moja ya vyama hivi eu kitaunda serikali.
Dah! Mie prediction yangu ilikuwa minority government Labour. Opinion polls zilikuwa zinaonyesha a tie between Conservative & Labour.