Thousands of opponents of Prime Minister Viktor Yanukovych blocked the entrances to Ukraine's Constitutional Court, prompting riot police to intervene to allow judges in.
The session began more than an hour late after helmeted police linked arms and formed a corridor to usher judges through a scrum of flag-waving demonstrators, who included rival lawmakers pushing and shoving each other outside the court's black metal gates.
Pro-Western President Viktor Yushchenko signed the dissolution decree on April 2, accusing his archrival Yanukovych of trying to usurp power. Yanukovych and his majority in parliament said the move was unconstitutional and appealed to the Constitutional Court.
The standoff has plunged this ex-Soviet republic into its worst political crisis since the 2004 protests that propelled Yushchenko to power and became known as the Orange Revolution.
Both Yushchenko and Yanukovych have agreed to abide by whatever the 18-judge court rules, but the bloc of former Premier Yulia Tymoshenko and political parties allied with Yushchenko have contended that the court is too corrupt to render a just decision.
The court has one month to rule, but increasingly it looks like even a court decision will not be enough to end the political paralysis seizing Ukraine. Tymoshenko, one of the leaders of the 2004 Orange Revolution, held a news conference Wednesday to tell her supporters "the time has come to appeal to Ukrainian citizens and patriots" to come to the streets again in protest.
She called on demonstrators to gather on European Square on Friday, saying it was time to repeat the actions of the 2004 Orange Revolution.
During those mass protests, Yushchenko rallied his supporters on Kiev's Independence Square to protest against Yanukovych's fraud-marred victory in the presidential vote, which was later overturned by the Supreme Court. Hundreds of thousands set up a sprawling tent camp that paralyzed central Kiev for weeks.
This time, Yanukovych's supporters have already staked claim to Independence Square, setting up camp there soon after Yushchenko signed his dissolution order.
Meanwhile, the Prosecutor General's Office acting under orders from Yanukovych warned lawmakers and protesters on Wednesday against trying to interfere with the work of the judges or prevent them from getting into the courtroom.
"We are standing here for justice," said Maryna Yeshchenko, 21, a Kiev student holding a Tymoshenko party flag a red heart on a white field. She was one of about 6,000 flag-waving demonstrators who support the president's dissolution order. Yeshchenko called on the judges to make a fair decision.
Yanukovych's supporters also brought out about 1,000 supporters to the courthouse. Denys Naunenko, 24, a miner from Yanukovych's hometown of Donetsk in eastern Ukraine, said he was there to demonstrate his opposition to new elections, which he called "shameful for Ukraine."
"It will hurt people's pockets," he said. "We want to become part of the European Union, but who will take us now?"
Also Wednesday, lawmakers from Yushchenko's parliamentary faction, Our Ukraine, and Tymoshenko's bloc said they would give up their parliamentary mandates _ an attempt to ensure that the legitimacy of the parliament would be questioned even if the Constitutional Court rules that Yushchenko's dissolution order was unconstitutional. It remained unclear, however, whether they could do that with the parliament technically dissolved.