He added that Russia could provide aid to the Middle East nation.
"This [100-150] is in the consular service's estimates," said Yury Brazhnikov, from the Emergency Situations Ministry. "Intensive efforts are being made at the moment to find Russian citizens in Lebanon."
Brazhnikov said Russians could be in regions in southern Lebanon controlled by the radical group Hizbollah, which abducted two Israeli soldiers last week giving Israel grounds for launching missile and air strikes on the country.
Brazhnikov suggested some of them might not have got registered with consular services.
Russia has evacuated 1,407 of its nationals and citizens of former Soviet Republics from Lebanon, the Russian Foreign Ministry said earlier Thursday.
"According to the Foreign Ministry's latest information, 1,407 citizens of Russia, and Belarus, Moldova and Ukraine, have been evacuated from Lebanon to Russia," a source in the ministry said.
Brazhnikov also confirmed an earlier report from the Foreign Ministry that Russia could provide humanitarian aid to the country.
"Lebanon has suffered a major damage, it will not cope on its own," he said.
Lebanon's prime minister has said more than 300 have been killed since Israeli missile and air strikes and hundreds of thousands have been forced to flee. Israel has destroyed almost all bridges and many crucial infrastructure facilities in Lebanon.
Israeli casualties from attacks mounted by militant group Hizbollah have been put at 29.
Israeli Ambassador to Russia Arkady Mil-Man said Thursday Israel was considering evacuating thousands of children from the north of the country.
"We will now try to evacuate at least 4,000-5,000 children from the northern regions of the country to central Israel so that they do not [have to] stay constantly in bomb shelters, which is hard both physically and mentally," he said.
