The US news agency Associated Press (AP) reported on the Serbian Parliament’s special session on Kosovo, saying that Serbia’s populist President Aleksandar Vucic faced a hostile reception from the right-wing opposition that accused him of treason.

The session included pushing and shoving, and shouting matches between Vucic’s ruling party and opposition lawmakers, said the agency.

Opposition MPs chanted “Treason, treason” and “We won’t give up Kosovo,” and demanded Vucic’s resignation, to which he responded by shouting at them that they are “thieves and traitors,” AP reported.

The news agency said that “during the chaotic parliamentary session” Vucic warned that Serbia could become a European “pariah” state if it rejects a Western plan for normalizing relations with Kosovo.

The Serbian President said that the plan, which hasn’t been made public formally, stipulates that Serbia wouldn’t object to Kosovo’s inclusion in international organizations, including the United Nations, though it wouldn’t have to formally recognize its statehood, AP reported.

The agency said that the “hard-line pro-Russia opposition lawmakers” described the Western plan for Kosovo as an “ultimatum,” claiming it would mean that Serbia would have to recognize Kosovo’s independence as a condition of eventually joining the European Union.