LONDON/GENEVA: More than 400 people were killed by cluster bombs in 2015 alone, most of them dying in Syria, Yemen and Ukraine, which have not signed up to a treaty banning the weapon, an international anti-cluster bomb coalition said Thursday.

Cluster bombs, dropped by air or fired by artillery, scatter hundreds of bomblets across a wide area which sometimes fail to explode and are difficult to locate and remove, killing and maiming civilians long after conflicts end.

They pose a particular risk to children who can be attracted by their toy-like appearance and colors.

In 2015, cluster bombs killed 417 people, more than a third of them children, the Cluster Munition Coalition said, adding that the actual number of casualties was likely to be much higher.

“The suffering is still continuing and civilians continue to be the predominant victims of cluster bombs,” said Jeff Abramson, program manager at Landmine and Cluster Munition Monitor, which is part of the coalition.

“Unfortunately now we’re seeing a new spate of people being injured at the time of attack, which is something that needs to be condemned very strongly,” he told Thomson Reuters Foundation by telephone from Geneva.

Abramson did not give figures for 2014, saying data was constantly being revised due to difficulties in gathering it, especially in conflict zones like Syria.

The coalition, made up of NGOs and led by Human Rights Watch, said the increased use of cluster bombs in Syria is linked to Russian forces carrying out airstrikes in support of President Bashar Assad’s regime.

“Since Russia began its joint operation with Syrian forces at the end of last September, we have seen an increase in the number of cluster munition attacks on opposition-held areas,” Mary Warenham, HRW’s arms advocacy director and editor of the report, told a news conference.

“And at the moment we see evidence of cluster munition attacks every week, if not almost every day, which is highly disturbing,” Warenham added.

Russia has repeatedly denied using cluster bombs.

HRW admitted it was difficult to determine whether it was specifically Russian or Syrian forces which had used the bombs.

“Nonetheless, this is a joint military operation, so collectively together they are responsible for the actions of their coalition,” Warenham said.

Syrian government forces have used at least 13 different types of cluster munitions produced by Russia and Egypt and some dated from the Soviet era, the report said.

Several of the cluster bombs dropped since Russian forces entered the Syrian war last year were produced in 1989-91, it added.

The report said this appeared to be “a noticeable shift” from before the Russian intervention, “when production markings on the cluster bombs used in Syria showed they were produced in the ’70s and ’80s.”

The majority of cluster bomb casualties in 2015 were in Syria (248), followed by Yemen (104) and Ukraine (19), the coalition then said in a report.

None of these countries, including Russia, are signatories of the Convention on Cluster Munitions, which prohibits the use, stockpiling, production and transfer of the weapons, it said.

The Convention, which came into force in 2010, also requires the destruction of stockpiles of cluster bombs and clearance of contaminated areas.

Since August 2015, five more countries – Colombia, Iceland, Palau, Rwanda and Somalia – have ratified the Convention, while Cuba and Mauritius acceded, bringing the total number of states that have signed or accepted the treaty to 119, the coalition said.

Casualties were also recorded in Laos, Lebanon, Afghanistan, Western Sahara, Chad, Cambodia and Nagorno-Karabakh.

The report was published ahead of the Sixth Meeting of states Parties to the Convention on Cluster Munitions that will be held in Geneva on Sept. 5-7.