MOSCOW (AP) — Russia’s foreign minister says reports about possible chemical weapons use by the Syrian regime should not be used as a pretext for a foreign invasion, saying a more thorough probe is needed.

Sergey Lavrov said Thursday that investigators must also look into claims of chemical weapons use by Syrian rebels.

France and Britain this week pointed at evidence that the nerve gas sarin was used by Syrian President Bashar Assad’s forces, signaling that Syria has crossed the "red line" set by President Barack Obama.

Lavrov warned against "speculations and provocation" surrounding the alleged chemical weapons use, saying the claims could be used by "certain forces, who may say that the red line has been crossed and that a foreign intervention is necessary."

Russia has been a key protector of Assad.