Ukraine's sustained campaign of drone attacks on Russian-occupied territories is disrupting Moscow's supply lines and intensifying a fuel crisis already triggered by long-range strikes on Russia's oil refineries.

Crimea - which Russia illegally annexed in 2014 - in particular has been experiencing serious logistical difficulties and shortages.

Many of the issues stem from recent Ukrainian strikes on a key motorway and bridge linking the southern Russian city of Rostov to Crimea via the occupied port city of Mariupol.

The road "is basically the backbone of Russian occupation in the south", Clément Molin, an analyst at the French-based think tank Atum Mundi, told the BBC.

Molin said that Ukraine had carried out 300 drone strikes on trucks, including 30 tankers, since the start of May and that the campaign had become more intense this month.

The operation is having tangible effects on Crimea. The peninsula is strategically important for Moscow, as it has been used by its forces to launch drones and missiles at the rest of Ukraine.

With its Mediterranean climate and long beaches, Crimea is also a popular holiday destination for Russians in the summer.

Disgruntled tourists and locals have taken to social media to vent about the disruption to fuel supplies.

Videos show long lines at petrol stations across the region, and residents have said they routinely have to queue for up to 10 hours for fuel.

"I walk to work now. Of course, this is less convenient than driving, but not a huge problem," one resident of the city of Simferopol told Bereg, an independent website. "All I've got to do now is buy a horse!" he added.

At the vast majority of Crimean petrol stations, locals are now only able to purchase up to 20 litres (4 gallons) of fuel each using prepaid vouchers, if it is available at all.

Russian tourists who arrived in the region before the start of the crisis are now struggling to find fuel to leave. The issue is acute enough that local Moscow-installed authorities have had to launch a special hotline to assist them.

There are also reports of skyrocketing petrol and diesel prices caused by the shortages.

"Unfortunately, it does not appear possible to fully satisfy the demand for fuel at the current moment," the Kremlin-appointed regional head, Sergei Aksyonov, admitted on 5 June. Hundreds of buses, he said, would not be leaving depots due to shortages.

Yet the roads remain the last way for supplies to reach the peninsula. The sea route is too dangerous, after a number of ferries serving Crimea were taken out of action by Ukraine.

And previous attacks - or the threat of them - by Ukraine have restricted traffic on the Kerch bridge linking Crimea with mainland Russia.

"I wouldn't want to put a truck full of diesel on the Kerch Bridge right now - that's just asking for trouble," Craig Kennedy, an expert in Russia's oil industry and associate at Harvard University's Davis Center, told the BBC.

"So you'll have to bring it in by land, via Mariupol. And there you're vulnerable all along the way."

Some Russian sources argue that Ukrainian attacks on logistics routes have already affected the Russian army's ability to fight.

"The strikes that empty fuel stations for civilians also affect supplies to troops in the south," Rybar, a pro-Kremlin Russian military analysis account , posted on its Telegram account.

"The logistics crisis does not distinguish between military and civilian needs, it hits everything at once."

On 7 June, a Ukrainian strike damaged a key bridge in Chohnar in northern Crimea, which linked it to the rest of Ukraine and was used by Russian troops and civilian vehicles travelling along the R-280 motorway. Traffic across the bridge has been suspended.

Problems with fuel supplies are made worse by Ukraine's long-range strikes against oil refineries and oil depots in Russia, which Kyiv has now been carrying out for several months.

President Volodymyr Zelensky said that nearly 40% of Russia's "primary oil refining capacity" was disabled in May because of such strikes.

Now, Craig Kennedy said, Ukraine's expanding campaign against Russia's supply network was seeing it move from targeting large refineries to smaller, local distribution networks.

"This is having a more focused or concentrated impact on local populations and the military in certain regions such as Crimea," he said.

Drone attacks have also affected other parts of occupied Ukraine, including the regions of Luhansk and Kherson.

Some have been carried out by the 413th separate battalion "Raid" of Ukraine's Unmanned Systems Forces, whose commander, Yevhen Karas, spoke to the BBC from an undisclosed location in Ukraine.

His drones, Karas said, did not encounter much resistance from Russian air defences during recent missions.

"It was a beautiful feeling when we can fly anywhere we want," he told the BBC.

According to Karas, disrupting Russia's military logistics is a key priority for his unit.

"The main dish is Russian storage, oil and fuel tanks, buildings and even small bunkers with Russian officers," he added.

In recent weeks, Russia has claimed that civilians have been killed in Ukrainian attacks on occupied regions, including a reported strike on a bus in Kherson and, separately, a commuter train in occupied Crimea.

On Monday, Aksyonov, Crimea's Russia-appointed leader, said a Ukrainian drone had again struck a passenger train in the region, killing its assistant driver and injuring the driver.

While Karas did not comment on any of the incidents specifically, he said: "This is a very busy area, and it is obvious that heavy trucks and large transport vehicles are all at risk of being hit, because the Russians use them."

Therefore, he added, "mistakes can happen, but this is not a deliberate targeting of civilian vehicles".

But the risks are too great, and as a result of the strikes, civilian movement on two key roads linking the occupied regions to Russia has too been restricted.

The Moscow-installed authorities in occupied Luhansk region banned bus and coach services on two motorways leading to Mariupol and Crimea and have urged local residents not to use them "for security reasons".

The combined effect of Ukraine's medium and long-range strikes not only affects Russia's ability to fight, but also serves Zelensky's declared purpose of "bringing the war home" to Russia.