After a three-way meeting in Moscow, the foreign ministers of Russia, Syria and Iran say their countries have agreed to intensify the fight against terrorism in Syria.

Russia's Sergey Lavrov made the statement on Friday after meeting with Syrian counterpart Walid al-Moallem and Iran's Javad Zarif.

Lavrov said at a news conference that the fight would come in parallel with efforts to improve humanitarian aid.

He also reiterated Russian denials that its warplanes were responsible for an attack on a school in Idlib province that the U.N. children's agency says killed 22 children and six teachers.

The Russian military on Thursday dismissed reports of the airstrike as a sham, citing images in the media showing desks standing intact next to a wall blown out allegedly by that very airstrike, while such an attack would have caused more extensive damage.