The Ukrainian Prime Minister has defied a presidential decree to dissolve parliament, which went into effect on Tuesday, and threatened to force an early presidential election. Prime Minister Viktor Yanukovich told an emergency session of parliament that the decree by President Viktor Yushchenko was a "fatal mistake" and urged legislators to keep working.

He later threatened to force an early presidential election if the president does not rescind the order dissolving parliament.

About 2,000 supporters of the Ukrainian prime minister streamed into the Ukrainian capital Tuesday to protest the president's order to dissolve parliament and call early elections.

Yanukovich's supporters expanded a tent camp outside the parliament while the president's supporters announced plans to setup a stage in Independence Square.

Ukrainian President Viktor Yushchenko signed the decree Monday and called a parliamentary election to take place on May 27.

The decree went into effect when it was published in the country's official gazette, though Yanukovich had urged the president to hold back from publishing the decree amid fears of deepening the country's ongoing political strife.

Lawmakers from Yanukovich's parliamentary coalition have appealed for a ruling by the constitutional court on the legitimacy of the president's order, the Interfax news agency reported.

The president and the prime minister were to hold discussions on the crisis on Tuesday afternoon.