Opposition lawmakers hurled eggs and smoke bombs inside Ukraine's parliament on Tuesday as the chamber approved an agreement allowing the Russian Navy to extend its stay in a Ukrainian port until 2042.
Crowds of supporters and opponents scuffled outside the parliament building as deputies from newly elected President Viktor Yanukovich's coalition approved a 25-year extension to the Russian Black Sea Fleet's base in Crimea.
"Today will go down as a black page in the history of Ukraine and the Ukrainian parliament," former premier Yulia Tymoshenko, now in opposition, told journalists inside parliament.
The chamber filled with smoke as the smoke bombs were released and Speaker Volodymyr Litvyn took shelter under umbrellas provided by bodyguards as eggs rained down on him. Protesting deputies unfurled Ukrainian flags across the benches.
The protests galvanised various opposition parties against Yanukovich for the first time since he was elected in February and they may yet prove a defining moment in the forming of an united opposition front.
They also highlighted the deep division in the ex-Soviet republic of 46 million. Yanukovich enjoys support mainly from Russian-speakers in the east and south, including Crimea, who lean more towards Moscow.
Ukrainian nationalists from the west and centre, led by Tymoshenko and former President Viktor Yushchenko, regard the base as a betrayal of national interests. They wanted to remove it when the existing lease runs out in 2017.
Deputies brawled and the chamber resounded to cries of "impeachment!", "coup!" "betrayal!" as passions ran high.
But, with the air still hazy from the smoke bombs, parliament ratified the lease extension by 236 votes -- 10 more than the minimum required for it to pass -- and then promptly adopted the 2010 state budget.
Parliament bypassed normal procedure and rushed through adoption of the budget without discussion because of the mayhem.
Yanukovich agreed the navy base deal with Russian leader Dmitry Medvedev on April 21 in exchange for a 30 percent cut in the price of Russian gas -- a boon to Kiev's struggling economy.
"There is no alternative to this decision -- because ratification means a lower price for gas and a lower price for gas means the budget," Prime Minister Mykola Azarov said.
"The budget means agreement with the IMF, the possibility of getting investments. It is a programme of development for Ukraine in the future."
Tymoshenko, speaking to a rally, said: "We have one slogan: Ukraine is not for sale. We must build a powerful system for the defence of Ukraine."
Former parliament Speaker Arseniy Yatsenyuk, who also ran for president, called for early parliamentary elections.
Yanukovich, speaking to journalists in Strasbourg where he attended a session of the Council of Europe, dismissed the disturbances, according to Interfax Ukraine news agency, saying: "Nothing unexpected took place in the Ukrainian parliament."
The Kremlin has presented the base deal as a diplomatic coup and Russia's lower house of parliament approved it with 410 of the 450 lawmakers voting for the deal under an hour after the Ukrainian parliament voted.
"The Black Sea fleet acts as a guarantor of security both in the Black Sea and in the Mediterranean Sea," Russian Defence Minister Anatoly Serdyukov said after the two votes.
The Russian fleet has been based in Sevastopol since the reign of Catherine the Great in the 18th century. But, under an accord after Ukraine gained independence following the break-up of the Soviet Union, the fleet would have had to leave in 2017.
Yushchenko, Yanukovich's pro-Western predecessor who favoured Ukrainian membership of NATO, pushed hard when he was in office for the fleet to be withdrawn.
But Yanukovich wants to improve ties with Ukraine's former Soviet master. He says the Black Sea fleet does not endanger Ukraine's national interests and enhances European security.
Yanukovich's opponents say he is acting against the constitution. But the constitution is ambiguous, containing two contradictory articles on foreign military bases in the country.
Nina Matviychuk, a 60-year-old pensioner, welcomed the move. "The Russian ships in Sevastopol are in a bad state and need repairing, building. It probably means more money for our factories. It will be work for us," she said in Kiev.
The Russian fleet in Sevastopol comprises 16,200 servicemen, a rocket cruiser, a large destroyer and about 40 other vessels.
Proponents point out that the Crimea was part of Russia until then-Soviet leader Nikita Khrushchev gave it to Ukraine in the 1950s. The region retains a Russian-leaning population.