The global chemical weapons watchdog has said the nerve agent sarin and toxic chemical chlorine were "very likely" used as weapons in two attacks in central Syria in March 2017.

The United States and Russia have agreed to work together on an international investigation of a Syrian chemical weapons attack last week that prompted retaliatory American missile strikes.

An international team has concluded that the Syrian government and Islamic State militants carried out chemical attacks in the conflict-hit nation during 2014 and 2015, according to a report.

The Islamic State group has launched two chemical attacks, killing a three-year-old girl and wounding some 600 people near the northern city of Kirkuk, Iraqi officials said.