Pushed to define "other terrorist groups," Lavrov said: "If it looks like a terrorist, if it acts like a terrorist, if it walks like a terrorist, if it fights like a terrorist, it's a terrorist, right?"
Lavrov was addressing reporters at the U.N. in New York Thursday, on the second day of airstrikes by Russian warplanes in Syria.
Moscow, which supports the regime of Syrian President Bashar al-Assad, has been accused of using the strikes to target anti-Assad groups including the U.S.-backed opposition group the Free Syrian Army (FSA).
But Lavrov said Russia does not consider the FSA a terrorist group. "We believe that Free Syrian Army should be part of the political process," he said.
"The goal of our operation -- in response to the request of President Assad and on the basis of the decision granted by the Russian parliament to the Russian President in accordance with the Russian constitution -- the goal is terrorism and we are not supporting anyone against their own people. We fight terrorism," Lavrov said.
Lavrov questioned the U.S.-led coalition's legitimacy, given the mission had not received the consent of the U.N. Security Council or any "request of one of the countries on whose territories they operate."
"You cannot avoid the impression that the legal basis of the coalition activities in Syria is really flawed," he said.
"As far as I understand, the coalition announced ISIL and other associated groups as the enemy and the coalition does the same as Russia [does]. Somehow some people try to present the coalition action as leading to a political settlement and Russia fighting the same people is being perceived or presented like defending the regime. It's absolutely unfair," he said.
The foreign minister also questioned the logic of trying to topple al-Assad to further the fight against ISIS, asking whether the removal of Saddam Hussein in Iraq and Moammar Gadhafi in Libya had made those countries better places.
Russia's Defense Ministry issued a statement earlier Thursday saying that it had carried out new airstrikes.
"Russian Aerospace Forces engaged another four #ISIS facilities in #Syria this night," the Ministry announced on Twitter along with gun camera video showing large explosions.
The strikes were carried out by eight Russian SU-24 and SU-25 jets, which claimed to hit ISIS "terrorist staff" and an ammunition dump near Idlib and another headquarters in Hama.
But 24 hours into the military campaign, there were concerns it was targeting those who oppose al-Assad, including more moderate factions that are supported by the United States and others in the West.
The Syrian Ambassador to Russia, Riad Haddad, told CNN's Matthew Chance that Russians were fighting alongside the Syrians, to destroy not just ISIS but all of the other rebel groups in Syria.
Haddad said all of the rebel groups, including ISIS, have a common goal: "to spread terror."
He told CNN that the impact of the Russian airstrikes over the past few days has been more effective than all of the coalition airstrikes so far combined and that the Syrian army and the Russian army are working side by side, sharing intelligence and data and working very closely together.
'Killing civilians in cold blood'
Wednesday's strikes were centered around the city of Homs, in western Syria
near the border with Lebanon.
A Syrian opposition activist living north of Homs near one of the villages targeted -- Talbiseh -- told CNN that ISIS had no presence in the area.
"Russian warplanes were targeting civilians and innocent people only, Putin is lying about targeting Daesh militants," Khdaier Khushfa said via Skype. Daesh is another name for ISIS.
"Daesh withdrew from the northern countryside of Homs in an announcement they made a year ago after the groups refused to deal with them, including Ahrar al Sham and Revolutionaries Front," he said.
"We know that Russia is the biggest ally of the Syrian regime, and since Bashar al-Assad considers us terrorists, then there is no doubt that Putin knows these areas are under our control and not Daesh."
Khushfa said the Russian strikes had killed 17 civilians in Talbiseh and 11 in Zafaraniya, despite rebel military posts and headquarters being located outside the two villages.
"We are used to the regime airstrikes but now the entire world is watching another country killing civilians in cold blood without taking any action," he said. "We are very concerned about what will happen next -- civilians I spoke to are very scared -- it's like, after five years since the revolution started we are back to ground zero."
McCain: Putin's goal 'to prop up Bashar al-Assad'
U.S. officials have also questioned whether ISIS is active in the areas hit by the Russian strikes.
Sen. John McCain -- chairman of the U.S. Senate Armed Services Committee -- told CNN's Chris Cuomo that he could "absolutely confirm" that the initial strikes were "against our Free Syrian Army or groups that have been armed and trained by the CIA, because we have communications with people there."
McCain called the Russian strikes "an incredible flouting of any kind of cooperation or effort to conceal what their first -- Putin's priority is. And that is of course to prop up Bashar al-Assad."
Defense Secretary Ash Carter said Wednesday that the Russian attacks, which the Kremlin said were meant to target terrorists, didn't appear to hit targets under the control of ISIS, which operates in the north and east of the country.
But the White House downplayed the dangers of the Russian move.
"I think the Russians have made clear that they're not interested in provoking a conflict," White House Press Secretary Josh Earnest said. "Their actions thus far indicate that that's what they believe."
The U.S. and Russian military will hold a secure video teleconference call Thursday. The U.S. will be represented by Elissa Slotkin, assistant secretary of defense for international security affairs, and Vice Adm. Frank Craig Pandolfe, director of strategic plans and policy on the Joint Staff, according to the Pentagon.
Iraq: Russian help 'beneficial'
The Iraqi Prime Minister welcomed Russia's involvement in the fight against ISIS.
"Well, of course it is beneficial," Prime Minister Haider al-Abadi said in an interview with PBS. "Don't forget, Iraq
was attacked from across the Syrian border into Iraq by Da'esh, by ISIL. And that cost us a lot of human costs in terms of people killed, people being kidnapped, people being enslaved, women, children."
For that reason, al-Abadi said, Iraq appreciated anyone willing to join the fight.
"Our message to the Russians -- I met with Putin -- please join this fight against Da'esh," he said, using another name for ISIS. "Da'esh is a dangerous terrorist organization, not only against Iraq, against Syria, against the whole region, against the whole world. It is time that we all join the same forces to fight Da'esh."
In his comments at the United Nations, Lavrov said that Russia had no plans to move its operations into Iraq.
"No we are not planning to expand our airstrikes to Iraq," he said. We are polite people -- we don't come if we are not invited."
Meanwhile, the Israel Defense Forces said Thursday that senior defense officials from Israel and Russia are scheduled to meet next Tuesday in Tel Aviv to address the coordination between the two militaries in the region. Israel's deputy chief of staff, Maj. Gen. Yair Golan, along with his Russian counterpart Maj. Gen. Nikolai Bogdanovski, are to meet at the Kirya Base in Tel Aviv, the IDF said.