Finland will join Nato on Tuesday, prompting Russia to boost military capacity

Finland will join Nato on Tuesday, marking the completion of a swift journey into the military alliance for the Nordic nation following Russia's invasion of Ukraine, officials said.

Finland has a 1,300-km (810-mile) border with Russia, meaning Nato's frontier with Russia will roughly double in length, and the move drew a pledge from Moscow that it will beef up its forces in border regions, reports Reuters.

"Tomorrow we will welcome Finland as the 31st member of Nato making Finland safer and our alliance stronger," Nato Secretary-General Jens Stoltenberg told reporters in Brussels, hailing the move as "historic."

"We will raise the Finnish flag for the first time here at Nato headquarters. It will be a good day for Finland's security, for Nordic security and for Nato as a whole," Stoltenberg said.

Finnish President Sauli Niinisto will travel to Brussels to take part in the ceremony, his office said.

Stoltenberg pledged to work hard to get Sweden into Nato as soon as possible. He also stressed that Nato and Swedish officials were already working to bring Sweden closer to the alliance even as they wait for membership to be finalised.

Moscow has responded by saying it will boost military capacity in its western and northwestern regions in response to Finland formally joining Nato, reports Al Jazeera.

Finland has a 1,300-km (810-mile) border with Russia that will roughly double the transatlantic alliance's frontier facing Moscow.

Russian Deputy Foreign Minister Alexander Grushko told state-owned news agency RIA, "We will strengthen our military potential in the western and northwestern direction. 

In the event that the forces and resources of other Nato members are deployed in Finland, we will take additional steps to reliably ensure Russia's military security."

Last year, Russian Defence Minister Sergey Shoigu said Russia was taking "adequate countermeasures" and would form 12 units and divisions in its western military district.

Wagner claims 'legal' control of Ukraine's Bakhmut

Russia's Wagner Group has claimed "legal" control of Ukraine's Bakhmut, but Kyiv said its forces still held the eastern town, describing the fighting there as "particularly hot."

Yevgeny Prigozhin, the head of the paramilitary force, said on Monday that his troops, involved in a months-long effort to encircle and capture the bombed-out town, had raised a Russian flag on its administrative building, reports Al Jazeera.

"From a legal point of view, Bakhmut has been taken. The enemy is concentrated in the western parts," Prigozhin said in an audio message posted on his press service's Telegram account.

But there was no indication from Ukrainian officials that Bakhmut, a town of 70,000 before the Russian invasion launched over a year ago, had fallen into Russian hands.

Prigozhin has previously made claims that were premature.

Ukrainian military leaders said on Monday after Prigozhin's video was released that enemy troops had tried to take control of the town, but their forces had "repelled more than 20 enemy attacks."

President Volodymyr Zelenskyy earlier on Sunday praised Ukrainian troops' defence of the city.

"Thank you to our soldiers who are fighting in Avdiivka, Maryinka, and Bakhmut," Zelenskyy said in his nightly video address. "Especially Bakhmut. It is especially hot there."

Ukrainian Deputy Defence Minister Hanna Maliar had earlier described the situation around the town as "tense". Ukrainian forces were defending their positions, and Russian forces were paying scant attention to losses as they attacked, Maliar said.

Al Jazeera could not verify the battlefield reports.

Ukrainian military commanders have said their own counteroffensive – backed by newly delivered Western tanks and other hardware – is not far off, but have stressed the importance of holding Bakhmut in the meantime.

Prominent Ukrainian military analyst Oleh Zhdanov said fighting had engulfed the centre of Bakhmut. Ukrainian forces had repelled 25 enemy attacks, but Russian forces had captured the AZOM metal plant, which Ukrainian troops had defended for days.

"The enemy is attacking the city centre from the north, the east and the south and is trying to take the city under its full control," Zhdanov, who has close ties to the Ukrainian military, said in a video shown on YouTube.

In Kostyantynivka, a town about 27km (17 miles) from Bakhmut, a "massive attack" of Russian missiles killed three men and three women and wounded 11 others on Sunday, Ukrainian authorities said.

The attack targeted residential areas where "ordinary civilians" were living, Zelenskyy said.

There was a large crater in a yard and windows were shattered from ground to top floors in two 14-storey tower blocks, while private homes nearby had smashed roofs, the AFP news agency reported.

In Russia, a well-known military blogger, Vladlen Tatarsky, was killed by a bomb blast in a Saint Petersburg café on Sunday in what appeared to be the second assassination on Russian soil of a figure closely associated with the war in Ukraine.

Russia's state Investigative Committee said it had opened a murder investigation into the blast, which wounded 25 people.

It was not immediately known who was behind the killing. Wagner's Prigozhin said he would "not blame the Kyiv regime" for it, but another leading Russian official pointed the finger at Ukraine without providing evidence.

A Ukrainian presidential adviser said "domestic terrorism" was breaking out in Russia.

Russia accuses Ukraine of blowing up war blogger Tatarsky, arrests woman

Meanwhile, Russia on Monday accused Ukraine of organising the murder of a prominent war blogger in a St Petersburg cafe and arrested a young Russian woman shown in a police video admitting delivering the bomb that killed him and injured over 30 others.

Ukraine, which did not take responsibility for Sunday's attack, blamed "domestic terrorism" for the murder of Maxim Fomin, a Russian military blogger and cheerleader for Russia's invasion of Ukraine who called himself Vladlen Tatarsky.

Darya Trepova, the 26-year-old Russian woman arrested over his murder, confessed in a video released by the interior ministry that she had brought in the figurine of a likeness of Tatarsky that exploded shortly afterwards, killing him.