WATCH: Parliamentarians fight over Ukrainian flag

A Slovakian lawmaker who brandished a Ukrainian flag got doused with water and slapped during a tense debate on a controversial defense treaty with the US, as thousands protested outside the parliament in Bratislava on Tuesday.

The Defense Cooperation Agreement has already been approved by the Slovak government, but the parliament – the Narodna Rada – still has to vote on it. At one point, debate spiraled into a showdown between lawmakers when two deputies opposed to the pact – Andrei Medvecky and Peter Krupa of the People’s Party Our Slovakia (LSNS) – unfurled a Slovakian flag at the speaker’s podium.

Miroslav Ziak of the Freedom and Solidarity (SAS) party – which supports the treaty – responded by bringing up a flag of Ukraine. He was joined by fellow SAS deputy Jana Bitto Ciganikova and they moved in front of the two LSNS members.

Video from the parliament shows Medvecky unscrewing a bottle of water, throwing it in Ziak’s face, and then dousing the Ukrainian flag. LSNS leader Marek Kotleba then ran up to the podium, snatched the Ukrainian flag away from Ziak and slapped the mask off his face.

Medvecky and Krupa were reprimanded by the speaker. Ziak later said he would file a police report against Kotleba for “stealing” the flag. Ukraine’s embassy in Bratislava also protested over the incident.

Meanwhile, thousands of Slovaks gathered outside the Narodna Rada waving national flags and banners that said “Stop USA Army,” AP reported. Police said they prevented some of the protesters from entering the building.

The bone of contention is an agreement that would allow the US to use two air bases, Malacky-Kuchyna near Bratislava and Sliac in central Slovakia, over the next 10 years, while giving Slovakia $100 million to modernize them.

Critics have argued that it would provoke Russia and enable the US to deploy nuclear weapons and perhaps station troops permanently in Slovakia. The US embassy and the coalition government insist, however, that the deal would “enhance security” of Slovakia and that 23 other NATO members have already signed similar treaties.

Slovakia joined both NATO and the EU in 2004, just 11 years after it became independent following the “velvet divorce” with the Czech Republic in 1993.