Ballistic missiles used by the Syrian regime of President Bashar al-Assad are killing many civilians, including children, an international rights group said on Monday.

These missiles "are hitting populated areas, causing large numbers of civilian deaths, including many children", said Human Rights Watch, which has investigated nine ballistic missile strikes that killed at least 215 people in six months.

Among those killed in nine attacks from February to July, 100 were children, said HRW, which has visited seven of the sites.

Such missiles have what the group described as a wide-area effect, and when used in populated areas cannot distinguish between civilian and military targets.

The New York-based watchdog said "military commanders, as a matter of policy, should not order the use of ballistic missiles in areas populated by civilians".

But the repeated use of such missiles in areas populated by civilians "strongly suggests that the military wilfully used methods of warfare incapable of distinguishing between civilians and combatants, a serious violation of international humanitarian law".

Many such missiles are being launched by the 155th Brigade in the Qalamun area northeast of Damascus, said HRW, echoing claims made by activists.

Citing the Military Balance 2011 publication of the International Institute of Strategic Studies, the group said the Syrian army stockpiles Scud missiles, variants of Scud missiles, SS-21 Tochka missiles, and Luna-M missiles.

HRW meanwhile cited the testimonies of activists and residents at the sites of several ballistic missile attacks.

After one such strike on Al-Nairab in the northern city of Aleppo, an activist who spoke to HRW said a whole family had been killed.

"He said that Hassan Yassin, his wife, and their seven children, all minors, died in the attack. Yassin and his family were at home during the attack, he said," the group reported.

Syria's war has killed more than 100,000 people , most of them civilians, the UN says. Millions more have been forced by violence to flee their homes.