Protests in Ukraine have been worsening, with thousands in the capital of Kiev calling for President Viktor Yanukovych to step down over his decision to reject a deal for closer ties with the European Union. Photos show protesters clashing violently with riot police. But this video drives home just how serious the crisis is getting.

On Sunday, protesters outside the president's office in Kiev tried to break the line of riot police guarding the building by charging them with a front-end loader, a piece of construction equipment that is colloquially (if not quite accurately) referred to as a bulldozer. It's not clear how they got the vehicle to the front lines of the protests. No one was hurt in the incident, reportedly because other protesters convinced the driver to back off. A short video, released by the government's interior ministry, captured the vehicle twice pushing right into the line of police before pulling back.

You can also see flashes of light; it's not clear what caused them, but protesters have reportedly been setting fire to some objects during the demonstrations.

The video is reminiscent of a protest movement in Yugoslavia in 2000, when demonstrators successfully toppled President Slobodan Milosevic's government. Those protests were later termed the "bulldozer revolution" for a pivotal moment during the clashes, when a protesting truck driver charged the state media building in an industrial wheel loader. (It was not actually a bulldozer but, like with Sunday's front-end loader, was termed as such in press accounts at the time.)

Here are a few more photos of the front end loader pushing into Sunday's clash in front of the president's office. These photos really drive home how serious things are getting.