President Vladimir V. Putin of Russia traveled to Mariupol, a surprise visit to the Ukrainian city that was the site of one of the bloodiest battles since Russia invaded last year, and the closest the Russian leader has been to the front lines in the east.

Mr. Putin flew by helicopter from Crimea and then toured Mariupol in Donetsk Province in the east, according to the state news outlet Tass on Sunday.

It was Mr. Putin’s second unannounced trip to Russian-occupied areas of Ukraine over the weekend, and was the closest the Russian leader has been to the front lines in the past year. His trip on Saturday to Crimea was timed to coincide with the ninth anniversary of Russia’s illegal annexation of the peninsula. The two high-profile visits were also defiant gestures from the Kremlin less than 48 hours after an international court issued a warrant for his arrest.

For months last year, Russia poured thousands of troops into Mariupol, home to Europe’s largest steel plant, and indiscriminately bombarded the city, which once housed nearly half a million people. Outnumbered and with fewer and less sophisticated weapons, Ukraine’s military hung on, eventually taking shelter in the city’s steel factory. Finally, Ukraine’s forces retreated, leaving the devastated city in Russian control.

The report from the state news outlet Tass referred to the surprise stop as “a working trip” for Mr. Putin to review construction and restoration work in the city.