Syrian and Russian jets are stepping up strikes on opposition forces in northern Syria in retaliation for the sudden offensive that has cost the regime control of the country’s second largest city, Aleppo.

Russia has carried out five consecutive air strikes targeting a refugee camp in a neighbourhood in Idlib, according to UK-based human rights group the Syrian Observatory for Human Rights (SOHR). The strikes killed at least one civilian and have injured others, the monitor says.

Syrian armed opposition forces have entered Aleppo just three days into their surprise offensive, marking the first time they have set foot in the country’s second largest city since government forces recaptured the city in 2016.