(CNN) -- Lawmakers in Ukraine scuffled with each other, throwing punches and eggs, as parliament met Tuesday to ratify a treaty with Russia that extends the latter's navy presence in the Ukraine's Crimean peninsula until 2042.

The ruling Regions party eventually ratified the treaty but not before howls of protest from the opposition.

Someone set off a smoke bomb inside the building, while Speaker Volodymyr Lytvyn sought refuge behind an umbrella as he was pelted with eggs.

During a rally attended by thousands on Saturday, opposition leader Yulia Tymoshenko -- the former prime minister who lost to Viktor Yanukovych in the presidential election run-off in February -- said the ratification must be prevented at all costs.

She claimed that Yanukovych is "selling out" Ukraine, has "openly embarked on the path of destruction of (Ukraine's) national interests, and has actually begun the process of eliminating the state's sovereignty."

The deal was signed last week by Yanukovych and Russian President Dmitry Medvedev.

Tymoshenko said it violated part of the Ukrainian Constitution, which forbids the country from hosting foreign military bases after 2017.

The deal extends Russia's lease of a major naval base in the Black Sea port of Sevastopol for an additional 25 years, in exchange for a 30 percent cut in the price of natural gas that Russia sells to Ukraine.

The agreement may bring an end to years of disputes over natural gas prices, which culminated in Russia turning off the pipeline to Ukraine.

The dispute affected not only Ukrainians, but many Europeans who depend on Russian gas pumped through Ukraine.

The two countries had been at odds ever since the "Orange Revolution" swept Yanukovych's fiercely anti-Russian predecessor Viktor Yushchenko to power in 2005.

Throughout his time in office, Yushchenko repeatedly threatened to expel Russia's Black Sea Fleet from Sevastopol. The Russian military lease there was scheduled to expire in 2017.

Yanukovych said the new deal added a "concrete and pragmatic dimension" to centuries of relations between Ukrainians and Russians.

Opposition groups in Ukraine, however, were quick to denounce the agreement. Yuschenko's "Our Ukraine" party said the treaty would lead to the "Russification" of Ukraine.