Zelensky Says Future of War in Ukraine Hinges on U.S. Presidential Election: Live Updates

The foundation, known by its Russian initials F.B.K., has regularly embarrassed senior Russian officials, including President Vladimir V. Putin, by exposing vast holdings they have accumulated while in office, far beyond what their government paychecks would allow.

The other American was arrested after arriving in Russia on July 27 and accused of trying to kidnap his 4-year-old son, a Russian citizen, and to spirit him across the border into Poland, according to a statement released on Thursday by the Investigative Committee, which did not name the man.

Regarding the teacher, the Russian government disbanded the Anti-Corruption Foundation in Russia in 2021 by declaring it an extremist organization, sending the group’s main investigators fleeing into exile, where they continue to work. Various Navalny supporters have faced criminal charges in Russia as the Kremlin has ratcheted up repressive measures, especially those trying to silence critics of its war in Ukraine.

A conviction for financing an extremist organization carries an eight-year jail sentence.

Mr. Startsev was born in Russia but moved to the United States as a child after his mother married an American, according to an interview he gave a few years ago as well as accounts in the Russian press. After moving to the Chicago area, he attended high school and Northern Illinois University, according to his online biography.

He moved back to Russia to pursue a teaching career. At the time of his arrest, he was teaching English for a Moscow company called the American Club of Education, which offers both online and in-person courses. He had also taught at a private school in Oryol, a provincial city more than 220 miles southwest of Moscow. He was jailed there on Thursday, a day after being detained in Moscow, Russian news media reports said.

There have been several recent cases of Americans being arrested on unlikely spying charges in Russia. Evan Gershkovich, a reporter for The Wall Street Journal, is incarcerated in Moscow facing trial, and Paul Whelan, 53, a former Marine, is serving a 16-year sentence. Last December, Brittney Griner, an American basketball star imprisoned in Russia on drug charges, was released after nearly 10 months of captivity in a prisoner swap for Viktor Bout, a convicted Russian arms dealer known as the “Merchant of Death,” who is now running for office.

On social media, Mr. Startsev made no secret of his staunch support for Mr. Navalny, who survived what is widely considered an attempt by government agents to kill him with poison, and has since been jailed in a Russian penal colony on various charges that have extended his sentence to at least 19 years.

In his last writing on VKontakte, the Russian equivalent of Facebook, Mr. Startsev lauded Mr. Navalny’s aims, and supported his vision of a “free, happy and uncorrupt future” for Russia, he wrote, with virtuous politicians being a key to this.

He had also posted a picture of himself on VKontakte, holding up a poster of what appears to be an opposition rally in May 2018. The dense, hand-lettered poster called for fighting corruption, poverty and inequality; restoring free elections; giving the opposition access to the media; releasing political prisoners; ending government control of the internet; and allowing the freedom of assembly.

In his 2019 interview, Mr. Startsev said he had used his time in the United States to improve his credentials in order to get a better job back in Russia. Asked about life in the United States, he said, “The food there has a different taste; the air is cleaner; the roads are better.”

He had learned a lot, Mr. Startsev said, but he wanted to apply it in Russia: “I want to help Russia become a great and beautiful country.”

In the other case, the Russian authorities are accusing the man of trying to take his son to live outside Russia without obtaining consent from the child’s mother, the office of the Investigative Committee in Kaliningrad said in the statement released on its Telegram channel. A criminal investigation has been started but no charges filed yet pending the man being questioned further, the statement said.

After arriving in Russia on July 27, the American met his son, who is a Russian citizen, the committee said. The boy lived in Kaliningrad, which borders the Baltic Sea and is Russia’s farthest point west. “Under the pretext of spending time together,” the man drove the boy in a car to a town near the Polish border and was detained while trying to cross it by walking through a swampy, wooded area, the statement said.

At the time of the incident, a court in Kaliningrad had been weighing where the boy should live, the statement said.

Milana Mazaeva contributed reporting.