US warns Russia against using nuclear weapons in Ukraine
Fourth day of voting in referendums on joining Russia
Ballot boxes taken door to door, says Ukraine
Heavy fighting continues along frontline
Russians protest against military draft
By Tom Balmforth
KYIV, Sept 26 (Reuters) - The Kremlin said on Monday no decision had been taken on whether to seal Russia's borders to stop an exodus of military-aged men fleeing the country, after days of chaotic scenes during its first military mobilisation since World War Two.
Asked about the prospect of the border being shut, Kremlin spokesman Dmitry Peskov told reporters: "I don't know anything about this. At the moment, no decisions have been taken on this."
Reports that Russia might close the frontier have contributed to turmoil since President Vladimir Putin gave the order last week to call up hundreds of thousands of reservists in the biggest escalation yet of the seven-month Ukraine war.
Flights out of Russia have sold out and cars have piled up at border checkpoints, with reports of a 48-hour queue at the sole road border to Georgia, the rare pro-Western neighbour that allows Russian citizens to enter without a visa.
"Everyone who is of conscription age should be banned from travelling abroad in the current situation," Sergei Tsekov, a senior lawmaker who represents Russian-annexed Crimea in Russia's upper house of parliament, told RIA news agency.
Two exiled news sites - Meduza and Novaya Gazeta Europe - both reported that the authorities were planning to ban men from leaving, citing unidentified officials.
The mobilisation was accompanied by an announcement by Putin that Moscow would stage votes to annex four Ukrainian provinces occupied by its forces. The West calls the votes, due to conclude on Tuesday, a sham pretext to seize territory captured by force.
The mobilisation has led to the first sustained protests in Russia since the war began, with one monitoring group estimating at least 2,000 people have been arrested so far. All public criticism of the "special military operation" is banned.
The past few days have also seen the first sustained criticism of the authorities on state-controlled media since the war began, with pro-Kremlin commentators denouncing officials for calling up people too old to fight.
On a talk show on Russia's main state channel, pro-Kremlin commentators demanded harsh punishments for draft officers who call up the wrong people.
"Can we just shoot them?" asked presenter Vladimir Solovyov. "I am in favour. I would just drag out a couple of those draft officers publicly," he said. "Grab that draft officer by the ear and send him to the front in the Donbas!"
Peskov acknowledged that some call-up notices had been issued in error, saying mistakes were being corrected by regional governors and the ministry of defence.
Russia counts millions of former conscripts as official reservists. The authorities have not spelled out precisely who is due to be called up - that part of Putin's order is classified - but have said they will draft 300,000 people, mostly with recent military experience.
Britain's Ministry of Defence said on Monday "many tens of thousands" of draftees had already received papers. They were expected to be sent swiftly to the frontline where they were "likely to suffer a high attrition rate", it said.
"The lack of military trainers, and the haste with which Russia has started the mobilisation, suggests that many of the drafted troops will deploy to the front line with minimal relevant preparation."
Images circulating on the internet have shown clashes between crowds and police, particularly in areas where ethnic minorities predominate, such as mainly Muslim Dagestan in the south and Buryatia, home to Mongol Buddhists, in Siberia.
More than 70 people were detained at protests against mobilisation in Makhachkala, Dagestan's regional capital, local news outlet Kavkaz Realii said. It said security forces used stun guns, batons and pepper spray against protesters.
Putin accompanied last week's announcement of the annexation referendums and the mobilisation with a barely veiled threat to use nuclear weapons to defend Russia's new territorial claims.
U.S. National Security Adviser Jake Sullivan said on Sunday the United States would respond "decisively" to any Russian use of nuclear weapons, and had privately told Moscow "exactly what that would mean".
Asked about Sullivan's comments, Kremlin spokesman Peskov said: "There are channels for dialogue at the proper level, but they are of a very sporadic nature. At least they allow for the exchange of some emergency messages about each other's positions."
The annexation votes are being held in Kherson, Zaporizhzhia, Luhansk and Donetsk provinces, territory equivalent to the size of Portugal.
None of those provinces is now fully under Moscow's control and fighting has been underway along the entire front line, with Ukrainian forces reporting more advances since they routed Russian troops in a fifth province, Kharkiv, earlier this month.
The exiled mayor of Russian-controlled Melitopol in the Zaporizhzhia region accused Moscow of forcibly enlisting Ukrainian men in occupied areas into its armed forces.
"Today the situation is critical: our residents are scared, our residents are panicking, they don’t know what will happen tomorrow and when they will actually take our people away for enlisting," Mayor Ivan Fedorov said.
"The voting takes place in front of assault rifles, men with weapons... People are grabbed right on the street and are forced to vote not only for themselves but for their whole families," he said via videolink from an undisclosed location.
The Ukrainian governor of Luhansk said Russian-backed officials were carrying ballot boxes from door to door, accompanied by security officials. Residents' names were taken down if they failed to vote as demanded, Serhiy Gaidai said.
Even traditional Russian allies such as Serbia and Kazakhstan have said they will not recognise the annexation votes. Moscow says voting is voluntary and turnout is high.
(Reporting by Reuters bureaus; Writing by Gareth Jones and Peter Graff; Editing by Toby Chopra)