Protesters in Brussels threw paving stones, road signs, fireworks, flares and other objects at police blocking their entry to an area where Michel's offices, other government buildings and the parliament are located. Brussels police spokeswoman Ilse Van de Keere said that around 400 protesters were gathered in the area. 

About 100 were detained, many for carrying dangerous objects like fireworks or clothing that could be used as protection in clashes with police.

The reasons for the protests are not entirely clear. Neither Belgium nor the Netherlands has proposed a hike in fuel tax -- the catalyst for the massive and destructive demonstrations in France in recent weeks.

Instead, protesters appeared to hail at least in part from a populist movement that is angry at government policy in general and what it sees as the widening gulf between mainstream politicians and the voters who put them in power. Some in Belgium appeared intent only on confronting police.