Russia cut off mobile internet services to many customers in Moscow on Tuesday ahead of the May 9 parade, due to the threat of drone attacks from Ukraine.
The Kremlin said the limits were introduced to ensure security amid a heightened risk of Ukrainian drone attacks.
Six Reuters reporters in Moscow confirmed that mobile internet did not work in different parts of the capital.
Russian mobile operators warned of possible mobile internet issues over the coming days.
This is the biggest drone war ever, with both sides targeting far behind front lines.