The Syrian government in March asked for a U.N. investigation into claims rebel forces used chemical weapons. The United Nations said it was ready for an investigation, though Syria later expressed reservations over its scope.
Lavrov said the Syrian government's concerns deserve to be honored nevertheless.
"We insist that the Syrian government's request should receive a response," he was quoted by state news agency RIA Novosti as saying from Hungary.
Syria says opposition forces killed at least 25 people during a chemical weapons attack in Aleppo province. The United States and some of its allies say there's preliminary evidence to suggest Syrian forces may have used small amounts of chemical weapons of their own, specifically the nerve agent sarin.
A U.N. investigation team is reportedly on standby in the region. U.S. State Department spokesman Patrick Ventrell said it was time for the Syrian government to open its doors.
"The Syrian government, if they've got nothing to hide, should allow their entrance into the country," he said.