"Pearl Square in downtown Manama: Tonight, it has become the center of a growing and increasingly organized protest," he said. "There appear to be tens of thousands of protesters here. Keep in mind that this is a country of less than a million people.
"The protests began Monday in mainly Shia Muslim areas on the outskirts of the city," he said. "At the time, the protesters wanted more work and opportunities from the Sunni-dominated government.
"But after two protesters were killed, the crowds and demands have grown stronger and bigger."
Protesters in Bahrain are demanding not just jobs but also the release of political prisoners, broad constitutional reforms and an end to the monarchy that has ruled Bahrain for 200 years.
King Hamad al Khalifa went on television to call for an investigation into the deaths and ordered police to back off.
"The result," said Marquez, "[is] thousands of protesters who say they won't leave the square until they get what they want.
"On Friday, there is a call for an even bigger demonstration. Organizers expect tens of thousands -- maybe more than 100,000 people to show up. At this point, this protest is only growing stronger."
ABC News' Jake Tapper, Emily Schmidt, Kirit Radia and the Associated Press contributed to this report.