WASHINGTON: Computer problems, as well as human ones, have drawn complaints across the US as millions of Americans go to the polls.

One Pennsylvania voter highlighted a problem with voting machines on YouTube, complete with video, in which a touchscreen changed his choice from President Barack Obama to Republican Mitt Romney.

"I initially selected Obama but Romney was highlighted," the man wrote. "I assumed it was being picky so I deselected Romney and tried Obama again, this time more carefully, and still got Romney."

This was not the first allegation of foul-ups with electronic machines. In Ohio, some Republicans claimed machines were changing Romney votes to Obama, while Democrats accused Republican state officials of installing untested "experimental" software at the last minute.