After Moscow terror attack, Russia steps up airstrikes on Ukraine; Poland activates air force (WATCH)

Ukraine's capital, Kyiv, and the western region of Lviv faced a "massive" Russian air attack, according to officials, prompting heightened readiness among Polish forces. Deadly aerial attacks between Russia and Ukraine have escalated, with Sunday's early morning strikes occurring following the Russian military's claim of seizing the Ukrainian village of Ivanivske west of Bakhmut.

Also read: Brave teen named 'Islam' saved over 100 lives during Moscow terror attack; lauded as 'hero' (WATCH)

Additionally, a terrorist attack on a Moscow concert hall on Friday, resulting in at least 150 fatalities, has further intensified tensions between the two adversaries. President Vladimir Putin has sought to link Kyiv to the attack, a claim denied by Ukraine, while the Islamic State has claimed responsibility.

“Explosions in the capital,” Kyiv’s mayor, Vitali Klitschko, posted on Telegram on Sunday. “Air defence is working. Do not leave shelters.”

Maksym Kozytskyi, the governor of Lviv region, stated that the Stryi district, situated south of Lviv near the Polish border, also faced attacks.

Earlier, Ukraine had been placed under a nationwide air alert, cautioning about the launch of cruise missiles from Russian Tu-95MS strategic bombers. However, the alert was lifted approximately two hours later.

Sergiy Popko, head of the Kyiv city military administration, reported that the missiles were launched at the capital "in groups" during the third pre-dawn attack in four days. Preliminary reports indicated no casualties or damage, with the city's air defenses successfully intercepting "about a dozen" missiles.

“The enemy continues massive missile terror against Ukraine,” Popko said on Telegram. “It does not give up its goal of destroying Kyiv at any cost.”

In Lviv, the mayor, Andriy Sadovy, said about 20 missiles and seven Iranian-made Shahed drones were fired at the region. “They targeted critical infrastructure facilities.”

The Polish Armed Forces Operational Command (RSZ) declared that its forces were on high alert due to the "intensive long-range aviation activity of the Russian Federation tonight" and the missile assaults in Ukraine.

“Polish and allied aircraft have been activated, which may result in increased noise levels, especially in the south-eastern part of the country,” it said.

Subsequently, it was reported that Russia had breached Poland's airspace with a cruise missile, which "entered Polish space near the town of Oserdow (Lublin Voivodeship) and remained there for 39 seconds."

“During the entire flight, it was observed by military radar systems,” it added.

Both Russia and Ukraine have escalated their air attacks in recent weeks.

Despite facing challenges in acquiring weapons and personnel after over two years of conflict, Kyiv has vowed to retaliate by extending the conflict into Russian territory.

According to the regional governor, multiple air attacks on Saturday targeted the Russian border region of Belgorod, adjacent to Ukraine, resulting in two fatalities and at least seven injuries.

Also read: Putin calls Moscow attack as 'barbaric terrorist act'; announces day of mourning on March 24 (WATCH)

Further to the east, a drone strike on the Samara region ignited a fire at a significant oil refinery, marking the latest assault on Russia's energy sector.

Vyacheslav Gladkov, governor of Belgorod, reported on Telegram that drone and air attacks struck two districts within his region, as well as the regional capital, Belgorod city. He stated that a man was killed when three balconies collapsed on an apartment building.

Russia later announced on Saturday that it had thwarted a barrage of Ukrainian missiles aimed at the city of Sevastopol in Crimea, which Russia annexed in 2014.

Sevastopol’s governor, Mikhail Razvozhayev, said rocket fragments had killed a 65-year-old resident and four other people had been wounded. “It was the biggest attack in recent times.”

Moscow has intensified its offensive by launching numerous missile strikes on Friday and deploying dozens of explosive drones to dismantle Ukraine's energy infrastructure.

Additionally, Russian forces have seized control of several frontline settlements in recent weeks.

The capture of Adviivka last month, situated near the Russian-held stronghold of Donetsk, marked Russia's first significant territorial advancement since the seizure of the devastated city of Bakhmut ten months ago.

Putin celebrated this achievement as an indication that Russian forces had resumed their offensive operations.