The attack, dubbed “Petya,” is a ransomware worm that has so far targeted, among others, Ukrainian banks and airports; Russian state-owned oil giant Rosneft; British advertising company WPP, US pharmaceutical giant Merck; and shipping company AP Moller-Maersk, which said every branch of its business was affected.
Companies across the globe are reporting that they have been struck by a major ransomware cyber-attack.
British advertising agency WPP is among those to say its IT systems have been disrupted as a consequence.
Ukrainian firms, including the state power company and Kiev’s main airport, were among the first to report issues.
The Chernobyl nuclear power plant has also had to monitor radiation levels manually after its Windows-based sensors were shut down.
CCTV cameras have captured the moment an underground water pipe exploded in the Ukrainian capital of Kiev.
The ground rises and shakes before bursting, sending earth and debris flying in all directions, and a torrent of muddy water down the street.
Cars were damaged and windows broken but no injuries were reported.
It is unclear what caused the pipe to explode on Monday.
NATO continues to support Ukraine with military equipment against pro-Russian rebels in Donetsk.
Ukrainian troops on Monday were battling a Russian tank contingent in the eastern city of Lugansk, Kiev said, accusing Moscow’s army units of moving into large cities in the region.
Hungary’s gas pipeline operator, FGSZ, says it has suspended delivery of gas to neighbouring Ukraine “indefinitely”.
Ukraine has been receiving gas from Hungary, Poland and Slovakia since Russia cut off supplies to Ukraine in June in a dispute over unpaid bills.
Ukrainian state gas firm Naftogaz confirmed the stoppage, saying it was “unexpected and unexplained”.
FGSZ said it had acted to raise the flow of gas to Hungary, due to an expected increase in demand.
With winter approaching fears are mounting that Ukraine will be unable to heat homes and power industry without Russian gas.
Russian and Ukrainian energy ministers are meeting in Berlin for EU-brokered talks, aimed at heading off such a crisis.
Relations between the former USSR’s two most populous countries soured after the overthrow of Ukraine’s pro-Russian President, Viktor Yanukovych, in February.
Russia subsequently annexed the Crimea region from Ukraine and was accused of fomenting a bloody insurrection in two of its eastern provinces.
Earlier this year Gazprom and Russian President Vladimir Putin warned of consequences if EU member states went ahead with deliveries to Ukraine to replace Russian supplies.
Russia says EU states are contractually forbidden from re-exporting gas to Ukraine while Brussels insists that such “reverse flows” are legal.
Hungary’s move came three days after a meeting in Budapest between the head of Russian gas giant Gazprom, Alexei Miller, and Hungary’s Prime Minister, Viktor Orban.
Prime Minister Orban has been critical of EU sanctions on Russia and has maintained a closer relationship with Moscow than his western European neighbours.
Gazprom agreed on Friday to boost supplies to Hungary, Reuters news agency reports.
“Hungary cannot get into a situation in which, due to the Russian-Ukrainian conflict, it cannot access its required supply of energy,” Mr Orban said on Hungarian state radio.
European Commission spokeswoman Helen Kearns said on Friday: “The message from the Commission is very clear: we expect all member states to facilitate reverse flows as agreed by the European Council
“There is nothing preventing EU companies to dispose freely of gas they have purchased from Gazprom and this includes selling this gas to customers both within the EU as well as to third countries such as Ukraine.”
Naftogaz urged its “Hungarian partners to respect their contractual obligations and EU legislation”.
“Neither EU countries nor Ukraine should be put under political pressure through energy blackmail,” Naftogaz said on its website.
It is hoped that Friday’s talks will establish a basis for an interim deal over energy.
The deal could involve the EU buying enough Russian gas to safeguard Ukrainian and European supplies during the winter months, at roughly market prices, according to Reuters.
However, Russian Energy Minister Alexander Novak insisted in an interview published on Friday that re-exporting Russian gas to Ukraine is illegal and could lead to some EU states going without fuel shipments from Gazprom.
“We hope that our European partners will stick to the agreements,” he told Germany’s business daily Handelsblatt (in German).
“That is the only way to ensure there are no interruptions in gas deliveries to European consumers,” he said.
In June, Russia cut off all gas supplies to Ukraine after Kiev failed to settle its debt with Gazprom.
Gazprom had sought $1.95bn (£1.15bn) out of a total claim of $4.5bn.
The Russia company said Ukraine had to pay upfront for its future supplies.
The issue of gas supply has dogged relations between Russia and Ukraine since the break-up of the USSR, with Russia seeking new export routes for its gas which would bypass Ukraine. EU supplies have been hit twice in the past decade because of the dispute.
The Kremlin has been accused of using Russia’s leverage as a major gas supplier for political ends in its international relations.
As Putin pushes Ukraine to bend to his will and allow greater independence to Russian-backed separatists in the country’s southeast, the Russian president holds a trump card: Winter is coming.
“I think that nobody thinks of [winter] anymore, except Russia,” Putin said on Sunday, according to The New York Times. “There are ways of helping resolve the issue. First, to immediately stop hostilities and start restoring the necessary infrastructure. To start replenishing reserves, conducting the necessary repair operations and preparing for the cold season.”
Geysar Gurbanov, a Rotary international world peace fellow currently at Harvard, recently explained the leverage that Putin has over Ukraine as the temperature drops.
“According to the U.S. Energy Information Agency, [Ukraine’s] primary energy consumption is fueled by natural gas (40%) and coal (28%),” Gurbanov writes in The Duke Chronicle. “With winter coming to Ukraine in less than four months and the coal mines located in the easternmost part of the country ravaged by conflict, Ukrainians will freeze in their homes as their gas supplies from Russia are depleted. Therefore, if the rebels fail to achieve their goal, Gazprom, Russia’s energy giant, will help Putin to win the war eventually.”
So Putin’s remark could be interpreted as a veiled threat signaling that if Ukraine’s army doesn’t back down against the separatists (and embedded Russian soldiers), then Moscow will use gas as a weapon.
In 2013, Russian gas accounted for half of the total gas consumed in Ukraine. On June 16, Russia cut off gas supplies to Ukraine over unpaid bills. Earlier this month, Gazprom said that Ukraine’s outstanding debt for gas supplies stood at $5.3 billion as of Aug. 1.
Russia has already said that Ukraine would have to prepay for future gas shipments unless Kiev begins payments on accumulated debts.
The EU is currently trying to broker a deal that would allow shipments to resume temporarily.
In any case, Putin has the upper hand as Ukraine’s gas reserves run out as winter sets in.
“Can Ukraine now survive without Russian gas? No, it can’t,” Ukrainian Prime Minister Arseniy Yatsenyuk said earlier this month, according to RIA Novosti. “How much Russian gas do we need to buy? About 5 billion cubic meters.”