VINNYTSIA, July 17 - President Volodymyr Zelensky fired state security service chief and prosecutor general on Sunday, citing hundreds of criminal proceedings into treason and collaboration by people within their departments and other law enforcement agencies.

“In particular, more than 60 employees of the prosecutor’s office and the SBU (state security service) have remained in the occupied territory and work against our state,” Zelensky said, The Associated Press reported.

“Such an array of crimes against the foundations of the state’s national security, and the links recorded between Ukrainian security forces and Russian special services raise very serious questions about their respective leaders,” he said in his nightly video address to the nation.

Zelensky dismissed Ivan Bakanov, a childhood friend and former business partner whom he had appointed to head the SBU. Bakanov had come under growing criticism over security breaches since the war began; Politico last month cited several unidentified Ukrainian and Western sources saying Zelenskyy was looking to replace him.

He also dismissed Prosecutor General Iryna Venediktova, and replaced her with her deputy Oleksiy Symonenko. Venediktova has helped lead war crime investigations.

Meanwhile, Russian missiles hit industrial facilities earlier Sunday at Mykolaiv, a key shipbuilding center in southern Ukraine. Mayor Oleksandr Senkevych said the missiles struck an industrial and infrastructure facility. Mykolaiv has faced regular

Russian missile strikes in recent weeks as the Russians have sought to soften Ukrainian defenses.

Early in the campaign, Ukrainian forces fended off Russian attempts to capture Mykolaiv, which sits near the Black Sea coast between Russia-occupied Crimea and the main Ukrainian port of Odesa. Since then, Russian troops have halted their attempts to advance in the city but have continued to pummel both Mykolaiv and Odesa with regular missile strikes.

The Russians, fearing a Ukrainian counteroffensive, also sought to reinforce their positions in the Kherson region near Crimea and in part of the northern Zaporizhzhia region that they seized in the opening stage of the war.

“Given the pressures on Russian manpower, the reinforcement of the south whilst the fight for the Donbas continues indicates the seriousness with which Russian commanders view the threat,” the British Defense Ministry said Sunday.

For now, the Russian military has focused on trying to take control of Ukraine’s eastern industrial heartland of the Donbas, where the most capable and well-equipped Ukrainian forces are located.

Ukraine says its forces still retain control of two small villages in the Luhansk region, one of two provinces that make up the Donbas, and are fending off Russian attempts to advance deeper into the second one, the Donetsk region.

The Ukrainian military’s General Staff said Sunday that Ukrainian troops thwarted Russian attempts to advance toward Sloviansk, the key Ukrainian stronghold in Donetsk, and attacks elsewhere in the region.

Yet Russian officials are urging their troops to produce even more territorial gains. During a visit to the front lines Saturday, Russian Defense Minister Sergei Shoigu issued an order “to further intensify the actions of units in all operational areas.” (ap/ez)