Thousands of protesters were expected to march in downtown Chicago today to the lakeside McCormick Place convention center where President Barack Obama and dozens of other world leaders will meet for the NATO summit.

Newlyweds Tim and Beth Alberts left the church in the city centre on Saturday after exchanging their vows and found themselves in the middle of a mass demonstration.

With her mouth open aghast at the sight of the anti-capitalist activists, a furious Beth Alberts was caught on video telling the wedding party: “Let’s get out of here.”

Newlyweds Tim and Beth Alberts left the church in the city centre on Saturday after exchanging their vows and found themselves in the middle of a mass demonstration

Both Chicago residents, Tim Alberts is a law clerk at Brady, Connolly & Masuda and Beth Alberts is a medical aesthetician at Cellular Intelligence Med Spa.

Hundreds of protestors paid little heed to the newlyweds on their march through the city. The anti-NATO protests were also aimed at Chicago Mayor Rahm Emanuel’s budget cuts.

There were high tensions and frequent clashes between protesters and police today as violence broke out in pockets around the city.

Police in riot gear surrounded the downtown areas of Grant Park and the Loop and also patrolled train stations.

Protesters began arriving at 6.30 a.m. at the park and set up under the trees to shade themselves from the sun.

Following the rally in the park, protesters planned to march to the convention center at McCormick Place. Around the NATO summit, concrete barriers have been set up along with black, anti-scale fencing. Some businesses and homes in the area have taken the precaution of boarding up their windows.

Chris Geovanis of the Chicago and New Media Collective told the thousands gathered in the park that police had interfere with the march and hurt some protesters, according to the Chicago Tribune.

The Reverend Jesse Jackson also appeared and said the protests must remain non-violent.

He said: “We learned from Dr. King in Birmingham. We march in a disciplined, non-violent way. We cannot afford to have our message hijacked by acts of provocation.”

There have been 18 arrested over the past week – not including the five people arrested on suspicion of two separate terrorist plots to use Molotov cocktails during the summit.