Ukraine admitted some Russian gains inside the eastern battlefield city of Bakhmut on Thursday but insisted it was inflicting greater losses on the Russian attackers than its own forces were taking in defense.
In a potential escalation of Russia's diplomatic feud with the United States, Moscow's FSB security service said it had arrested an American reporter for The Wall Street Journal, Evan Gershkovich, on suspicion of spying for Washington.
The small mining city of Bakhmut has been the site of the bloodiest infantry battle in Europe since World War II as Russian forces have sought their first victory since mid-2022 in a huge winter assault.
Ukraine has been on the defensive for nearly five months but says it is planning a counteroffensive soon.
"Enemy forces had a degree of success in their actions aimed at storming the city of Bakhmut," the General Staff of the Ukrainian armed forces said in an overnight report. "Our defenders are holding the city and are repelling numerous enemy attacks."
The report gave no details of the Russian gains. The Institute for the Study of War think tank said Russian troops and Wagner mercenaries had captured territory in the south and southwest of the city over the past two days, and Wagner had occupied a metal plant in its north this week.
Russian forces have been advancing slowly inside Bakhmut in the intense street fighting for weeks. Kyiv seemed likely a month ago to abandon the city but has since decided to stay and fight for it, hoping to break the attacking force.
Deputy Defense Minister Hanna Malyar said in a social media post that losses were inevitable, but "the enemy's losses are many times greater."
Serhiy Cherevatyi, a Ukrainian military spokesperson, told national television: "Bakhmut remains the epicenter of military activity ... It's still constantly 'hot' there."
As winter has turned to spring, the pressing question is how much longer Russia can sustain its offensive, and when or if Ukraine will strike back.
There are signs its campaign is slowing down. The number of daily Russian attacks on the front line reported by Ukraine's general staff has declined almost by half over the past four weeks.
Reporter arrested
The arrest of Gershkovich could have an impact both on diplomacy with the United States and on international coverage of Russia and the war.
He would be the highest profile American arrested by Russia since basketball star Brittney Griner, who was caught arriving in Moscow with cannabis oil a week before the invasion of Ukraine and freed in a prisoner swap in December.
The FSB said in a statement it had "stopped the illegal activities of U.S. citizen Gershkovich Evan, born in 1991, a correspondent of the Moscow bureau of the American newspaper The Wall Street Journal, accredited at the Russian Foreign Ministry, who is suspected of spying in the interests of the American government."
No comment was available from the newspaper.
The FSB said Gershkovich had been tasked "by the American side" with gathering information on "the activities of one of the enterprises of the military-defense complex." It provided no evidence.
The U.S. Embassy's travel guidance, last updated in February this year, advises U.S. citizens not to travel to Russia because of the danger of arbitrary arrest and says U.S. citizens living or traveling in Russia should depart immediately.
Moscow has effectively outlawed all independent Russian news outlets since the start of the war but has continued to accredit some foreign reporters. Journalism has become sharply limited by laws that impose long sentences for any public criticism of the war.