In a second week of protests against President Viktor Yanukovich's decision to abandon a trade deal with the EU in favour of closer ties with Russia, demonstrators feared the arrival of riot police heralded a plan to crush them by force.
Police gave the protesters five days from last Thursday to leave the streets. Protesters said they will not go.
Liberals and nationalists have taken to the streets for demonstrations that have at times drawn hundreds of thousands. Thousands have also maintained an around-the-clock protest camp in the city centre, blocked roads, besieged government buildings and occupied the capital's city hall.
The police managed to avoid violence while pushing protesters back from positions around some government buildings.
Yanukovich is expected to meet the EU foreign affairs chief later on Tuesday as well as three former Ukrainian presidents who have proposed talks. The moves are among the president's first apparent concessions since the crisis erupted.
Ukraine's dire finances have both provoked the crisis and been worsened by it. EU leaders say their trade pact would have brought investment. But Ukraine's Soviet-era industry relies on Russian natural gas, giving the Kremlin enormous leverage.
Presented by Adam Justice