Russian President Vladimir Putin declared martial law on Wednesday in the four regions of Ukraine that Moscow annexed last month while ordering all of Russia to support the war effort.
He also granted additional emergency powers to the heads of all regions of Russia to come into effect on Thursday.
His decree gives law enforcement agencies three days to submit specific proposals and orders the creation of territorial defence forces in the four annexed regions.
Russia annexed Luhansk and Donetsk in eastern Ukraine and in Zaporizhzhia and Kherson in the south, following disputed votes there.
“We are working to solve very difficult large-scale tasks to ensure Russia’s security and safe future, to protect our people,” Mr Putin said in televised remarks at the start of a Security Council meeting on Wednesday.
“Those who are on the front lines or undergoing training at firing ranges and training centres should feel our support and know that they have our big, great country and unified people behind their back.”
The upper house of Russia's Parliament was set to quickly seal Mr Putin’s decision to impose martial law in the annexed regions.
Draft legislation indicates it may involve restrictions on travel and public gatherings, tighter censorship and broader authority for law enforcement agencies.
Mr Putin has not yet provided details of the extra powers to be given to the heads of Russian regions under his decree.
“In the current situation, I consider it necessary to give additional powers to heads of all Russian regions,” he said.
The Russian leader also ordered the establishment of a co-ordination committee to increase interaction between various government agencies in dealing with the fighting in Ukraine — which he and other officials continue to call a “special military operation”.
“Putin’s decree in effect brings several Russian regions on the border with Ukraine into the perimeter of the war,” said Alexander Baunov of the Carnegie Centre.
“It looks like a trial run of emergency mechanisms in several regions that can then be expanded to other territories.”
Governors of the affected regions were quick to play down any immediate impact.
Moscow Mayor Sergei Sobyanin said, “at present, no measures that would restrict the normal rhythm of life in the city are being imposed.”
Kremlin spokesman Dmitry Peskov said Mr Putin’s order does not envisage the closure of Russia's borders, state news agency RIA Novosti reported.
Earlier on Wednesday, the new commander of Russian forces in Ukraine made a rare acknowledgement of the pressures they were under from Ukrainian offensives to retake southern and eastern areas that Moscow says it annexed just weeks ago.
“The situation in the area of the special military operation can be described as tense,” Gen Sergei Surovikin told the state-owned Rossiya 24 news channel.
On Kherson, Gen Surovikin said: “The situation in this area is difficult. The enemy is deliberately striking infrastructure and residential buildings.”
Russian forces in the Kherson region have been driven back up to 30 kilometres in the past few weeks and are at risk of being pinned against the western bank of the 2,200km Dnipro river that bisects Ukraine.
Vladimir Rogov, a member of the Russian-installed council governing Zaporizhzhia, said Ukraine's forces had intensified overnight shelling of Russian-held Enerhodar — the town where many employees of the Zaporizhzhia nuclear power station live.
Artillery fire had hit the town's outskirts and there had been 10 strikes around a thermal power station, he said on the Telegram messaging app on Wednesday.
Earlier on Wednesday, the Russian-installed chief of Kherson region, Vladimir Saldo, said about 60,000 people would be evacuated in the next six days.
The city of Kherson had a pre-war population of around 280,000 people but many of them have since fled.
He said up to 40 per cent of civilians in the Kherson region were being moved to steer clear of the fighting.
“No one is going to hand over Kherson," he said.
"But it is not ideal for residents to be in the city where hostilities will take place."
Kherson is the biggest population centre Moscow has seized and held since it began its "special military operation" in Ukraine on February 24.
Ukrainian presidential adviser Mykhailo Podolyak said less than a month had passed “since the pompous announcement of Kherson annexation and solemn concert on the Red Square, as the self-proclaimed 'city administration' … ceremoniously evacuates in anticipation of Ukrainian justice. Reality can hurt if you live in a fictional fantasy world”.
A senior Ukrainian official accused Russia of organising a “propaganda show” in Kherson.
Andriy Yermak, head of the Ukrainian president's office, also accused Russia of “trying to scare the people of Kherson with fake newsletters about the shelling of the city by our army, and also arrange a propaganda show with evacuation”.
“Propaganda will not work,” he wrote on the Telegram messaging app.
