Officials in Russia on Monday issued a warning to truck drivers threatening demonstrations that have seen roads blocked across the country in a rare mass protest rattling the authorities.
"Our job is to ensure unhindered and safe daily travel on federal roads at any time of day," the head of Russia's road agency Roman Starovoit said in a statement.
"Anyone who intends to sabotage the traffic flow on roads in our country will face suitable measures from the law enforcement agencies."
Truck drivers around Russia are up in arms over a tax hike introduced earlier this month that saw higher levies slapped on heavy vehicles after the authorities said they should effectively pay for wear and tear on the roads.
The protests -- which have seen long lines of lorries cause major disruptions around the country -- have gone largely unreported by Russia's state media, which seeks to play down any sign of discontent against President Vladimir Putin's rule.
The government -- struggling to cope with an economic crisis caused in part by the fall in oil prices and Western sanctions over Ukraine -- was hoping to raise some 40 billion rubles (570 million euros, $600 million) with the new tax in 2016.
But the move has sparked widespread ire from truckers that has been targeted at the son of a close ally of Putin, Igor Rotenberg, who part-owns a firm responsible for collecting the tax.
Truckers from around the country had earlier said they planned to converge on Moscow on Monday but reports in independent media outlets and on social media said some had been blocked by police.
Alexander Kotov, the head of a drivers' union, told TASS news agency the protesters had decided to "give the government and lawmakers time to react" but warned that demonstrators could still make for Moscow later in the week.
After initially trying to brush off the protests, the government has struck a more conciliatory tone in recent days by pledging to review the size of the tax and any fines for non-payment.
"Why are the authorities silent on the truckers' protest and not trying to discredit them with deceitful TV reports as usual?" wrote opposition leader Alexei Navalny in a blog post.
"It is because this protest has popular support and the anger of the protesters is directed at the circle closest to Putin. Any word they say will make the situation worse for the Kremlin and help the truckers."