Three hours into Egypt's constitutional referendum, we're hearing reports of high turnout - and potential irregularities.

Voters have reported long lines (see the photos below), with some predicting an hours-long wait to cast their votes. That's mostly been viewed as a positive development, a sign of high voter enthusiasm - a major change from last year's fraudulent parliamentary election, which saw turnout as low as 10 per cent in some parts of the country.

But some voters are reporting a more serious problem: unstamped ballot papers.

Each ballot needs an official stamp on the back, or it can be thrown out as illegitimate. What we're hearing is that some polling centres in Cairo and its suburbs are distributing unstamped papers. In some cases, election judges will (when asked) provide stamped papers in other cases, they refuse, offering instead to sign the ballots - which does not legitimize them.

Here's a photo of how the stamp should look: The green heading says "stamp of the committee," and underneath is an ink stamp from the local election committee.

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We've heard these reports of unstamped ballots in Giza, Mohandiseen, 6th of October City, as well as several polling centres in Alexandria.

Here are a couple of photos of queues that have been posted online the first is from Giza, the second from Cairo:

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