KYIV, Dec 23 (AFP) - Ukrainian President Volodymyr Zelenskyy has warned his country of possible increased Russian attacks over the upcoming Christmas holiday season, urging his people to “pay attention to air raid alarms, help one another and look out for one another”.

In his regular nightly video address on Friday, Zelenskyy said that he had met his top military commanders to review the situation and that his government is “preparing for various scenarios of action by the terrorist state. And we will respond”.

“With the holiday season fast approaching, the Russian terrorists could again step up their activities,” Zelenskyy said. “They have no regard for Christian values or any values for that matter.”

The Ukrainian leader also issued an unusually sharp warning to Russia.

Switching to Russian, Zelenskyy warned that “citizens of Russia must clearly understand that terror never goes without a response”.

He did not elaborate.

In recent days, the Ukrainian military leadership has repeatedly warned of possible new missile attacks on the country’s infrastructure and energy supply, which has already been devastated by drone and missile attacks in recent weeks, leaving millions without power, heating and running water.

On Friday, Ukraine’s military said that a Russian naval unit was under way in the Black Sea, including a warship equipped with cruise missiles, and Moscow is also sending in troop reinforcements to the front lines in eastern and southern Ukraine, according to Ukrainian intelligence.

“The enemy has increased the volume of rail transport of troops, equipment and ammunition to the combat areas,” the general staff in Kyiv announced on Friday. The main combat areas were the surroundings of the front-line town of Bakhmut in the east, as well as the localities of Avdiivka, Kupiansk and Limansk in the Donbas region.

Reinforcements on the Russian side were also detected in the south of the country, the general staff said.

Visiting the Russian arms manufacturing centre of Tula on Friday, President Vladimir Putin told defence industry chiefs to increase production and ensure that Russian forces quickly received all the weapons, equipment and military hardware needed to fight in Ukraine.

Russian Defence Minister Sergei Shoigu on Friday also visited the Kalashnikov arms factory in Izhevsk and told its director that the state would “significantly increase” orders from the plant next year, the Zvezda military news channel said

A trade union leader in Russia’s Urals region told the state-owned TASS news agency last week that companies involved in defence orders there had moved to a six-day week with workers on shifts of up to 12 hours.

“The most important key task of our military-industrial complex is to provide our units and front-line forces with everything they need: weapons, equipment, ammunition, and gear in the necessary quantities and of the right quality in the shortest possible timeframes,” Putin said in Tula.

Despite Kyiv receiving billions of dollars of Western weapons along with military intelligence, Putin has said that Moscow will prevail despite fierce Ukrainian resistance and nothing would alter the outcome of his war in Russia’s favour.