Chechen units should relieve the Wagner forces in the battle for the fiercely contested Ukrainian city of Bakhmut, the head of the Russian paramilitary group urged Moscow on Saturday.

Wagner chief Yevgeny Prigozhin called for the Akhmat battalion, led by Chechen leader Ramzan Kadyrov, to take over the Bakhmut positions by midnight on May 10, in a letter to Defense Minister Sergei Shoigu dated Saturday and posted on Telegram.

Prigozhin has threatened to pull the mercenary force out of Bakhmut amid a striking breakdown in relations between the Russian government and the paramilitary group. In a statement published Friday, Wagner commanders said Russian defense ministry units were supposed to back up the Wagner group’s flanks, but were struggling to do so.

The commanders accused the Kremlin of artificially creating supply shortages and mass casualties. Prigozhin himself posted a video ranting from the front lines about fallen fighters.

Kadyrov had offered to take over the position on Friday, according to AFP. Prigozhin replied on Saturday, saying the Akhmat battalion would “no doubt” take Bakhmut.

Also on Saturday, the Ukrainian military confirmed that it had shot down a hypersonic Russian missile over Kyiv earlier in the week — the first time Ukraine has been known to intercept one of Moscow’s most sophisticated weapons.

The Russian missile was downed using the newly acquired Patriot missile defense system, after Ukraine received the long-sought, American-made defense batteries from the U.S., Germany and the Netherlands.

“Yes, we shot down the ‘unique’ Kinzhal,” Air Force Commander Mykola Oleshchuk said on Telegram, referring to a Kh-47 missile, which flies at 10 times the speed of sound. “It happened during the night time attack on May 4 in the skies of the Kyiv region.”

Separately, a well-known Russian nationalist writer was injured in a car bombing, Russian state-owned outlet TASS reported. Zakhar Prilepin was wounded in the blast in the Russian city of Nizhny Novgorod, according to the report.

Meanwhile, Switzerland’s parliament approved a request from Kyiv for Ukrainian President Volodymyr Zelenskyy to address the Swiss assembly, Reuters reported. The invitation, announced late Friday, comes amid pressure on Switzerland’s government to end a ban of exports of Swiss weapons to conflict zones such as Ukraine.

This article has been updated.