"I do not dare say any formal, standard things related to expressing condolences," he said.
He added that some news reports about Moscow's offensive in Ukraine could not be trusted.
"There is a lot of fake news, deceit and lies," he said.
Putin, who has introduced legislation that effectively bans any public criticism of the offensive in Ukraine, told the women they should be wary of what they read on the internet.
"It is clear that life is more complex than what is shown on our TV screens or even on the internet, nothing can be trusted there," he said.
Earlier on Friday, Putin's spokesman Dmitry Peskov said the rest of the discussion would be shown "depending on the conversation."
State television aired images of the Russian leader sitting at a table with 17 mothers, in the first such meeting since Putin sent troops to Ukraine on February 24.
"I completely understand that for you, and for many other women in Russia whose sons are currently in fighting zones, this will not be a festive time," the 70-year-old said, referring to Mother's Day.
Videos of Russian mothers and relatives concerned about men fighting in Ukraine have in recent months flooded Russian social media.
