The effect Barack Obama's presidency has had on the number of 'patriot' militias in the US

A group of around a dozen armed men took over a federal building on a wildlife reserve in Oregon on Saturday.

The armed protesters, who have decided to call themselves the “Citizens for Constitutional Freedom” say they are protesting against government tyranny and are demanding that the land be handed over to local ranchers - although their lack of snacks and supplies has proven problematic.

Research by the Southern Poverty Law Center in 2014 assessed the rise of anti-government, or "patriot", groups over the past few years.

This chart by Statista shows the number of these groups, which had been at a previously low level during the Bush presidency, spiked after Barack Obama's election:

In Oregon in 2014, 19 anti-government groups were found by the non-profit organisation.

Here's the number of groups by state, as found by a 2014 report:

However, as the organisation points out, their research shows that militias (as opposed to other anti-government groups who do not engage in military-style training) have been declining in recent years.