President Vladimir Putin on Sunday ordered stronger border security to ensure "fast" Russian military and civilian movement into Ukrainian regions now under Moscow control.
Speaking in a congratulatory message to the border service, a branch of Russia's Federal Security Service (FSB), on their Border Guard Day holiday, Putin said their task was to "reliably cover" the lines in the vicinity of the combat zone.
Attacks inside Russia have been growing in intensity in recent weeks, chiefly with drone strikes on regions along the border but increasingly also deep into the country, including on an oil pipeline northwest of Moscow on Saturday.
"It is necessary to ensure the fast movement of both military and civilian vehicles and cargo, including food, humanitarian aid building materials sent to the new subjects of the (Russian) Federation," Putin said in a message posted on the Kremlin's Telegram messaging channel.
Kherson, Zaporizhzhia, Luhansk and Donetsk are the four regions in Ukraine that Putin proclaimed annexed last September following what Kyiv said were sham referendums. Russian forces only partly control the four regions.
On Saturday, officials said three people were injured in Ukrainian shelling in Belgorod, a region that was the target of pro-Ukrainian fighters this week that sparked doubts about Russia's defense and military capabilities.
The Kursk and Belgorod Russian regions bordering Ukraine have been the most frequent target of attacks that have damaged power, rail and military infrastructure, with local officials blaming Ukraine.
Kyiv almost never publicly claims responsibility for attacks inside Russia and on Russian-controlled territory in Ukraine, but said that destroying infrastructure is preparation for its planned ground assault.
Ukraine indicated on Saturday that it was ready to launch a long-promised counteroffensive to recapture territory taken by Russia in the 15-month long war, a conflict that has claimed the lives of thousands and turned Ukrainian cities into rubble.