The fight broke out on Thursday evening as a debate about the place of the Russian language in the country descended into chaos.

Members of President Viktor Yanukovych's party - which has much of its support in the largely Russian-speaking south and east of the country - fought openly with the pro-Western opposition.

Video footage showed one lawmaker attacking the speaker of the assembly. About 10 others were seen punching each other, with one of the men restrained in a head lock.

At least one politician, opposition lawmaker Mykola Petruk, was taken to the hospital with blood streaming down his face after an apparent blow to the head.

The former Soviet state is divided along linguistic lines, with the Russian-speaking part of the country favoring greater ties with Moscow. Yanukovych has said he wants to make Russian the second language but pro-Western opposition critics are opposed.

The opposition has demanded an investigation into the violence.

Tensions are particularly high following the jailing of former prime minister Yulia Tymoshenko on charges the opposition and the West say are politically motivated.

There have been several brawls in the Ukrainian parliament in recent years. In one widely televised debacle in April 2010, opposition lawmakers were seen throwing eggs and smoke bombs to protest against a naval pact with Russia.

At least six politicians were treated in hospital after a fight later that year, which saw members of the ruling party throw chairs at opponents for allegedly trying to block the assembly's work.

rc/tj (AFP, AP)