Fifty NBP activists were arrested when they tried to enter the State Duma to attend a parliamentary session, citing the Constitution, which says parliamentary sessions are open to the public.
"Those arrested have been taken to a police precinct in Kitai Gorod [in central Moscow]," a police officer said.
The party's press secretary, which is led by the controversial writer Eduard Limonov, who earlier was himself charged with attempting to seize power and organize a mass disturbance, said 50 party members, also known as limonovtsy, converged on the lower house of parliament.
"This fall, the State Duma will adopt many crucial bills and amendments -- on the budget, insurance, education, real estate and wages," Alexander Averin said. "These laws must not be adopted without the oversight of the people."
In late September, NBP members burst into the Finance Ministry, throwing leaflets and demanding that bank deposits lost in 1990s be returned to their owners. Witnesses said the trespassers injured a security guard.
A Moscow court banned the organization last June, saying it violated the law on political parties by calling itself a "party" without being officially registered.
In December 2005, 31 NBP activists received suspended sentences, and eight others were sentenced to prison terms ranging from one and a half to three and a half years, for inciting public disturbances when they broke into the presidential staff's visitors' room in December 2004 to protest President Vladimir Putin's political reforms.
Lawyers filed an appeal with the European Court of Human Rights, saying the trial was unfair and biased.
