Hungary's prime minister Viktor Orban on Tuesday imposed a new state of emergency in the country, citing the challenges posed by the ongoing war in neighbouring Ukraine.

Hungary is already under a state of emergency, linked to the COVID pandemic, which was due to expire next Tuesday.

"The world is on the verge of an economic crisis. Hungary must stay out of this war and protect the financial security of its families," the nationalist leader said on Facebook, in comments that raised fresh concerns about the restriction of rights.

"This requires room for manoeuvre and immediate action. The government, exercising its right under the Basic Law, declares a state of emergency due to war as of midnight," Orban added.

Shortly before the announcement, the Hungarian parliament, which had just been sworn in, amended the constitution to allow for such a measure.

Orban's Fidesz party commands a two-thirds majority in the chamber. 

Rules decided under the new law change will be announced on Wednesday, Orban said.

The Hungarian Civil Liberties Union (TASZ) denounced the move, saying that "the state of emergency that has become permanent".

The move gives Orban "more leeway than usual", allowing him to "restrict or simply suspend everybody's fundamental rights," the group said, slamming what it described as the marginalisation of parliament.

Orban, in power for 12 years, is regularly accused by his Western partners of abuses of power in his country, a member of both the European Union and NATO.