A senator who oversaw the most violent period in the Philippines’ war on drugs has dismissed the killing of a three-year-old girl in a police drug operation as collateral damage, stating that “shit happens”.

Ronald dela Rosa, who was the police chief running President Rodrigo Duterte’s crackdown on drugs before he was elected as a senator two months ago, defended the shooting by police during a sting operation last week.

“We are living in an imperfect world,” Dela Rosa said on Thursday. “Would a police officer want to shoot a child? Never, because they have children as well. But shit happens during operations.”

He said the three-year-old, named Kateleen, had been used as a human shield by her father, a suspected drug dealer, during the police raid in a province east of the capital, Manila. Two suspected drug dealers and an undercover police officer were also killed in the operation.

A police spokesman, Bernard Banac, also defended the actions of the police and said the girl’s father had pulled a gun on officers first. “It cannot be helped if there was an accident,” Banac said. “He used his daughter as a human shield.”

The girl’s mother disputes this version of events. Twenty police officers have been suspended and an investigation is ongoing.

Kateleen is thought to be one of the youngest victims of Duterte’s violent crackdown on drug dealers in the Philippines. Since 2016 police have had unprecedented powers to track down and if necessary shoot-to-kill any suspects.

The official death toll in the drug war stands at just over 5,000, including dozens of children, though this falls well short of estimates given by human rights groups and campaigners for victims, which vary from 12,000 to 20,000. Rights groups say many of the undocumented killings were carried out by “death squads” and unofficial militias.

The international criminal court (ICC) is carrying out preliminary investigations into Duterte to determine whether his drug war may constitute crimes against humanity. On Thursday more than a dozen countries formally called on the United Nations human rights council to open an investigation into the war on drugs in the Philippines.

Duterte’s spokesman said this week that the calls for an investigation were “outrageous interference” by “foreign propagandists”.