KIEV, Ukraine (AP) — Thousands of Ukrainians angered by police violence and the president’s turn away from Europe headed for the center of the capital on Sunday, in what was expected to be the largest rally since mass protests started three weeks ago.

President Viktor Yanukovych’s meeting on Friday with Russian President Vladimir Putin has raised fears among the opposition that Ukraine is on the verge of entering a Russian-led customs union that critics say would recall the Soviet Union.

Authorities have said police won’t take action against peaceful demonstrators, but concerns persist that some opposition activists may be goaded into violence.

The opposition branded Sunday’s demonstration the "march of a million," calling on Ukrainians to protest police brutality and any deals that Yanukovych makes with Russia. The protest was to take place on the landmark Independence Square, known as the Maidan, and which was the site of the 2004 pro-democracy Orange Revolution.

"Go to the Maidan!," the opposition party of jailed former Prime Minister Yulia Tymoshenko wrote on Twitter. "We will chase him (Yanukovych) until he falls."

The demonstrations began after Yanukovych shelved the signing of an agreement to deepen ties with the European Union in order to focus on Russia, which worked aggressively to derail the EU deal.

During a huge demonstration a week ago, several hundred radical protesters hurled stones and attacked police as they tried to storm the presidential office, prompting a violent break-up by the authorities, in which dozens were injured, including peaceful protesters, passersby and journalists.

Yanukovych has been reluctant to free Tymoshenko, his top opponent. The EU condemned her jailing as political and demanded her release for the signing of the treaty.