KYIV, Ukraine — Russia announced increased security measures Saturday in the border region of Kursk, where an incursion this week by Ukrainian forces caught Russian troops off guard and exposed its military vulnerabilities in the nearly 2 1/2-year-old war.

President Volodymyr Zelenskyy appeared to refer indirectly to the operation in his nightly address Saturday, the closest a Ukrainian official has come to acknowledging it.

Zelenskyy commended Ukrainian combat brigades across the front line, including the Sumy region, which lies adjacent to Kursk.

He also said Gen. Oleksandr Syrskyi, the commander of Ukraine’s armed forces, had sent him multiple reports about the front-line situation “and our actions to push the war out into the aggressor’s territory.”

Fighting was continuing in the Kursk region and Russia is sending reinforcements to counter Ukraine’s raid, including rocket launchers, artillery and tanks, Russia’s Defense Ministry said.

About 76,000 residents were evacuated, a Russian Emergencies Ministry spokesman said Saturday.

There was fighting on the outskirts of Sudzha, 6 miles from the Ukraine border. The town has an important pipeline transit hub for Russian natural gas exports to Europe.

The measures announced for Kursk, and for the neighboring Belgorod and Bryansk regions that border Ukraine, allow the government to relocate residents, control phone communications and requisition vehicles.

The raid that began Tuesday is the largest cross-border foray of the war and raises concerns about fighting spreading well beyond Ukraine.

The strategic aims of the daring Ukrainian operation are unclear and there is little reliable information. Ukrainian officials have refused to comment on the incursion, which is taking place 320 miles southwest of Moscow.

Five days after it was launched, Ukrainian officials have remained quiet about the operation, but some Ukrainian soldiers appeared to break with that policy of silence by posting videos and photos on social media.

In one video posted late Friday, soldiers holding a Ukrainian flag appear to be standing outside a Gazprom facility in Sudzha, based on sign in the background.

Mathieu Boulegue, a defense analyst at the Chatham House think tank in London, said the Ukrainians appear to have a clear goal, even if they’re not saying what it is.

“Such a coordinated ground force movement responds to a clear military objective,” Boulegue said. Also, the raid has spooked the Russian public and delivered a slap in the face to Russian President Vladimir Putin, offering Ukraine “a great PR coup,” he said. The attack “is a massive symbol, a massive display of force (showing) that the war is not frozen.”