Satellite images show increased activity at a nuclear test site in northern Russia, according to an expert. The images, taken by the commercial satellite company Planet Labs, show that there has been a significant increase in the number of vehicles and personnel at the site in recent weeks.The expert, who spoke to The Associated Press on condition of anonymity, said that the increased activity is likely a sign that Russia is preparing for a nuclear test. The expert said that the activity is similar to what was seen at the site in the lead-up to Russia's last nuclear test in 2017.The Russian government has not commented on the increased activity at the test site. However, the Russian Foreign Ministry has said that Russia is committed to the Comprehensive Nuclear-Test-Ban Treaty, which bans all nuclear explosions.The Comprehensive Nuclear-Test-Ban Treaty has been signed by 185 countries, but it has not been ratified by the United States or China. The treaty bans all nuclear explosions, including those for peaceful purposes.The United States has accused Russia of violating the Comprehensive Nuclear-Test-Ban Treaty in the past. In 2019, the United States said that Russia had conducted a nuclear explosion at the test site in northern Russia. Russia denied the accusation.The increased activity at the nuclear test site in northern Russia is a cause for concern. It is a sign that Russia may be preparing for a nuclear test, which would be a violation of the Comprehensive Nuclear-Test-Ban Treaty. The United States and other countries should urge Russia to comply with the treaty and to refrain from conducting any nuclear tests.