Turkey warned on Monday it may bring in the army to help quell nationwide anti-government protests as two major union federations went on strike over police violence against demonstrators. The presence of soldiers on the streets would mark a major escalation of a crisis that has raged for nearly three weeks and poses the biggest challenge yet to Prime Minister Recep Tayyip Erdogan's Islamic-rooted government.

German Chancellor Angela Merkel said Monday that she was shocked by Turkey's violent crackdown on protests in major cities, saying it "was much too harsh". "There were horrible images in which one could see that the approach was much too harsh in my view," Merkel told commercial broadcaster RTL in reaction to news coverage of riot police breaking up demonstrations in Istanbul and the capital Ankara. "What is happening in Turkey at the moment does not meet with our ideas of freedom of assembly, (or) freedom of expression," she said. "I am in any case shocked."

Germany on Sunday urged Turkey to "respect the freedom to demonstrate and freedom of expression," in a tweet by government spokesman Steffen Seibert. "The German government has warned several times: freedom to demonstrate and freedom of expression must be guaranteed and peaceful citizens respected," the spokesman said, reacting to the latest violence in Turkey. In another tweet, Seibert said there should be "a continuation of dialogue" in Turkey, adding: "The German government again calls on all parties to reason".

Tens of thousands of Turkish government supporters were expected in Istanbul Sunday, hours after police stormed a city park to clear it of opponents of Prime Minister Recep Tayyip Erdogan. Riot police used tear gas and water cannon late Saturday to reclaim Gezi Park from demonstrators occupying what had become the symbolic heart of nationwide anti-government protests. The officers moved in just two hours after Erdogan issued an ultimatum to the protesters telling them to quit the park.