Beirut: Moscow on Thursday denied any involvement in bloody air strikes on a Syrian school as its relations with the West took another hit and the EU slapped more sanctions on its ally Damascus.
UN Secretary-General Ban Ki-moon demanded an immediate probe into Wednesday's attack on the school in rebel-held Idlib province that he said "may amount to a war crime".
The tensions mounted a day after the United States and Britain said they expected an assault to drive the Islamic State jihadist group out of Raqa, its de facto capital in Syria, within the next few weeks.
Syria's conflict broke out in March 2011 with peaceful protests against President Bashar al-Assad's government but has evolved into a complex war involving regional and international powers.
One complication has been the involvement of Turkey, whose President Recep Tayyip Erdogan announced today that his country's military operation supporting opposition fighters in Syria will also target Raqa.
Russia, whose military intervened in Syria in September last year, denied having played any role in air strikes on the school that the UN children's agency UNICEF said killed 22 students and six teachers.
"The Russian Federation has nothing to do with this terrible tragedy, with this attack," foreign ministry spokeswoman Maria Zakharova said, adding that Moscow demanded an immediate investigation.
Zakharova said claims that Russian and Syrian warplanes had conducted the deadly air strikes in Idlib on Wednesday were "a lie".
According to the Syrian Observatory for Human Rights monitor, "warplanes - either Russian or Syrian - had carried out six strikes" in the Idlib provincial village of Hass, including on a school complex.
On a nearby front, Russia's defence ministry said today that Syrian and Russian warplanes had not bombed Aleppo in the past nine days.
A ceasefire meant to allow civilians and armed combatants to leave rebel-held eastern Aleppo ended at the weekend, with Moscow on Monday ruling out an extension of the unilateral measure for the time being.
Idlib province is controlled by the Army of Conquest, an alliance of rebel groups and jihadists including the Fateh al-Sham Front, which changed its name from Al-Nusra Front after breaking off ties with Al-Qaeda earlier this year.
Syrian and Russian warplanes regularly bomb Idlib, but air strikes have intensified in recent weeks, according to the Observatory.
Children were reportedly caught in the crossfire again on Thursday, with Syrian state media saying at six were killed and 15 wounded in rebel rocket attacks on the government-held west of Aleppo city.
The rocket fire in Aleppo hit two neighbourhoods in the west of the divided northern city, with one of the attacks striking a school, said the SANA state news agency.