"The actions of the Russian air force, in response to the request of the Syrian leadership – have really helped to turn around the situation in the country, helped towards reducing the territory controlled by terrorists," Lavrov said at his main annual press conference.
Russia began a bombing campaign in September last year to fight terrorist groups seeking to topple its longstanding ally Assad. Last year its pilots carried out more than 5,000 sorties.
Forces backing Assad have recently made several key gains on the ground.
Government forces backed up by several dozen Russian airstrikes overnight captured the militant stronghold of Sheikh Miskeen close to the border with Jordan, the British-based Syrian Observatory for Human Rights said Tuesday.
Russian planes from Friday to Sunday carried out 169 flights, bombing almost 500 targets, the Russian defense ministry said Monday.
Lavrov also said that it is impossible to reach a peace agreement in Syria without inviting Kurds to take part in the negotiating process, saying that it would be "unfair" and "counter-productive" to stop them from taking part in the peace talks, Reuters reported.
Talks aiming to end the brutal war that has lasted almost five years are set to begin in Geneva Friday after delays due to disagreements over who would represent the splintered opposition, United Nations envoy Staffan de Mistura told reporters.