KIEV (AFP) - Human Rights Watch on Thursday accused both government and rebels forces of using cluster bombs in eastern Ukraine, with at least 13 civilians killed by the weapons since the start of the year.

"Using cluster munitions shows utter disregard for civilians," said Ole Solvang, senior emergencies researcher at Human Rights Watch (HRW).

"Neither side should use these widely banned weapons; they affect a large area, endangering nearby civilians, and unexploded submunitions pose a risk to civilians long after the attack." The US-based rights group said it had evidence both sides to the conflict in eastern Ukraine had used the weapons in January and February of this year, killing at least 13 civilians, including two children.

HRW urged both sides to join the 2008 Convention on Cluster Munitions prohibiting the use of such weapons.

"Ukrainian and Russian authorities seem to agree that it is unacceptable to use this weapon in populated areas," Solvang said. "Their actions need to match their rhetoric." Ukraine has denied using cluster munitions in the conflict.

Kiev and its allies in the West accuse Russia of arming and spearheading the pro-Kremlin uprising in the east. Moscow denies the allegation.

The United Nations estimates that more than 6,000 people have been killed in fighting since April. A ceasefire signed on Feb 12 has largely held despite some sporadic clashes.