Ukraine's President Viktor Yanukovich is set to return to work on Monday after a period of sick leave, a statement on the presidential website said. Thousands of anti-government protesters have gathered in central Kiev to demand his resignation.
Former boxing champion and Ukrainian opposition leader Vitaly Klitschko was sprayed with fire extinguisher powder during protests in the capital.
The 42-year-old was hosed down after trying to stop rioters attacking police in Kiev during demonstrations against new anti-protest laws.
Klitschko said: "Ukraine is united as never before in its struggle. We will not allow a dictatorship."
Ukraine has experienced difficult days before but few have been so complex or so pivotal.
The Ukrainian government says it is is ready to use all tools available to restore order if violence and unrest continues.
These are difficult days for Ukraine, a country edging toward its second revolution in a decade.