Some 30 MPs from opposition parties also disrupted parliamentary work in a further show of opposition to President Viktor Yushchenko's intention to seek membership in the Western military alliance for Ukraine, a one-time Soviet republic and the largest country completely in Europe.
The protesters in Kiev chanted slogans such as "NATO is slavery for Slavs" and "No to NATO!"
Last week, Ukrainian Foreign Minister Volodymyr Ohryzko handed a request for Ukraine to join NATO's Membership Action Plan to the alliance's secretary general, Jaap de Hoop Scheffer. The Action Plan is a necessary step on the path to eventual full membership of the organization.
Earlier on Friday, members of the Party of Regions and the Communist Party of Ukraine called on the country's leadership to recall the request for NATO membership, claiming that such a step was only possible after a referendum.
Prime Minister Yulia Tymoshenko previously stated that a decision on whether Ukraine should take up any future NATO offer to join the alliance would only be taken after a national referendum.
Ukraine's leadership hopes that a decision on its membership application will be taken in early April in Bucharest during a NATO summit meeting.
A recent poll carried out by Ukraine's Democratic Initiatives foundation reported that over 50% of Ukrainians would vote against joining NATO. In the survey, 51.9% of respondents said they viewed NATO as an "aggressive imperialist bloc that would draw Ukraine into military conflicts."