"Of course, neither in ceasefire agreements, nor in the process of political settlement is there a place for terrorists and extremists," Lavrov told the UN Human Rights Council in Geneva.
"A very special task is to cut the terrorists' supply from the outside. For this purpose it is important to close the Syrian-Turkish border, since across this border those gangs receive arms, including with humanitarian convoys," Lavrov said, according to an official transcript in English of his remarks.
His comments came after aid workers on Monday made the first delivery of desperately-needed assistance since the start of Syria's fragile ceasefire four days ago.
Moscow and Washington drafted the UN-backed cessation of hostilities deal, and the two countries are co-chairing an international task force evaluating how the ceasefire is holding.
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At an earlier meeting in Geneva, UN Secretary General Ban Ki-moon thanked Lavrov for "his significant role in achieving recent progress on Syria," a UN statement said.
The deal meanwhile does not apply to the vast swaths of territory held by the Islamic State group and Al-Qaeda affiliate Al-Nusra Front.
It is meanwhile hoped that the flow of much-needed assistance could create a more favourable backdrop for peace talks that collapsed in acrimony in early February.
UN envoy Steffan de Mistura aims to relaunch negotiations on March 7 if the ceasefire lasts and more aid is delivered.