Nepal was urged Friday to investigate the dozens of deaths that happened during protests by ethnic groups against the country's new constitution.

Human Rights Watch, a New York-based human rights group, said in a report that at least 45 people have died since the protests began in August and that the violence included "extrajudicial killings by the police against protesters, killing of children and murders of police officers."

Those killed included at last nine police officers attacked by protesters.

The rights group said Nepal should make sure that security forces do not use excessive force against protesters.

The government should establish an independent body to investigate the deaths and prosecute the perpetrators, the group said, adding protest leaders should make sure the protests are peaceful and ensure that those responsible for serious crimes are brought to justice.

Ethnic minority groups, mainly the Madhesi in the south and southeast and Tharu in the southwest, have been protesting since Nepalese lawmakers began to finalize the much-delayed constitution, which was approved by the country's Parliament on Sept. 20 despite the protests.

The Madhesi groups blocked several border points, and India, which supports the groups, blocked the flow of trucks bringing in fuel and other supplies to Nepal. That created a severe fuel shortage and threatens to disrupt Hindu festivals to be held this month.

The Madhesi group says the constitution unfairly divides Nepal into seven states with borders that cut through their ancestral homeland in the southern plains. The Madhesis, along with several other small ethnic groups, want the states to be larger and to be given more autonomy over local matters.