Cluster munitions have been used in five countries during 2015 posing a devastating threat to civilian populations caught in conflict zones, according to Human Rights Watch.

Coinciding with the release of this year’s Cluster Munition Monitor report, the human rights group revealed that Libya, Sudan, Syria, Ukraine, and Yemen have all used the munitions which are banned by 117 countries under the Convention on Cluster Munitions treaty.

None of these five countries have signed the treaty which imposed the ban due to the widespread and indiscriminate effect of the weapons and their resulting long-lasting danger to civilians.

These weapons can be fired by artillery and rocket systems or dropped by aircraft and typically explode in the air sending dozens of smaller bomblets or submunitions over a large area. These submunitions often fail to explode on initial impact causing them to act like land mines, posing a threat to civilians even after fighting has come to an end.

“Cluster munitions are banned weapons that shouldn’t be used by anyone under any circumstance because of the harm to civilians at the time of attack and long afterward,” said Mary Wareham, arms division advocacy director at Human Rights Watch and an editor of the report. “Those who use cluster munitions should stop immediately, and join the international ban without delay.”

According the the Cluster Munition Monitor 2015 report, which reviews the adherence by all countries to the treaty, the ban has had a significant effect on the eradication of the weapons and it has led to many nations joining and destroying their stockpiles.

States who have joined the ban have destroyed a total of 1.3 million stockpiled cluster munitions containing 160 million submunitions. This represents the destruction of 88% of all cluster munitions and 90% of all submunitions declared as stockpiled by the nations who have signed.

While the report says that there have been no reports of the weapons being used by any of the member states since it came into effect on 1 August 2010, Human Rights Watch has expressed concern over draft proposals by Australia, Canada, and the United Kingdom – all states that have signed the treaty – to water down language that condemns new use of cluster munitions.