It is the third time Britain has gone to the polls in two years, twice for a general election and once for the EU referendum, and voter fatigue appeared to be an issue among the early voters.
"I don't think it has really been a campaign, we don't know anything about what they are going to do about Brexit, it's been pointless really," said Joe Kerney, 53, at a polling station in Hackney, east London.
"I have little confidence in anybody," added voter Simon Bolton, 41. "I think we lack quality in terms of who we can choose, it is very limited." (AFP)
Security on voting day was reviewed following the London attack, with the city's Metropolitan Police force implementing a "specialist and highly flexible operation" which it said could be deployed as needed.
Polling stations, many located in schools and community centres, opened at 7:00am (0600 GMT) and will close at 10:00pm, with 49.6 million registered voters electing a total of 650 MPs to parliament.
An exit poll will give an indication of the outcome, although final results will not emerge until early Friday. (AFP)