"Kira Yarmysh and Ruslan Shaveddinov have been detained," tweeted Navalny, saying they would both spend the night at a police station.
The pair were arrested at a Moscow airport on Tuesday while returning from abroad, the opposition chief said.
A court hearing is scheduled for Wednesday.
Heeding a call by Putin's bete noire, thousands of Russians on Sunday staged rallies in dozens of cities to protest March elections widely expected to extend the Russian leader's Kremlin term to 2024.
Authorities had warned Russians against taking part in unsanctioned rallies.
Police broke into Navalny's Moscow headquarters using a saw in order to interrupt a marathon live broadcast of the rallies, but Yarmysh and Shaveddinov kept reporting from an undisclosed location.
Navalny himself was detained soon after he appeared at a Moscow rally on Sunday but was released later that day.
Several members of Navalny's team and supporters were however detained and sentenced to short jail terms.
Last year Navalny served three jail sentences of 15 days, 25 days and 20 days for organising unauthorised protests.
If Putin wins a fourth presidential term, he will become the longest-serving Russian leader since dictator Joseph Stalin.
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