Indian police have arrested five people, including two policemen, over the alleged gang-rape and murder of two teenage cousins, officials have said.
The three suspects, detained for the attack in Uttar Pradesh state, are cousins in their 20s from an extended family.
They face charges of rape and murder, crimes punishable by the death penalty, police officer N Malik said on Saturday.
Officials in Uttar Pradesh, which has a reputation for lawlessness, also arrested two police officers and sacked two others on Friday for failing to investigate reports of the girls' disappearance earlier in the week.
News of the gang-rape was accompanied by TV footage of the corpses of the teenage girls swaying as they hung from a mango tree, causing outrage across the nation.
'Enough is enough'
Sohan Lal, the father who reported the girls missing, has demanded a federal investigation.
"I don't expect justice from the state government as state police officers shielded the suspects," said Lal, a farm labourer who refused to accept a payment for 500,000 rupees ($8,500) offered by the state government as financial help.
On Saturday he said to reporters that he would accept no help until the Central Bureau of Investigation, India's FBI, takes over the investigation.
The state government led by Chief Minister Akhilesh Yadav has agreed to a CBI investigation, the DNA reported.
On Saturday, dozens of members of the All India Democratic Women's Association marched through the streets of New Delhi, India's capital, demanding justice for the victims.
"Enough is enough. Women will not tolerate such atrocities any longer," the protesters chanted.
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Ashish Gupta, a state inspector general of police, told journalists that 10 rapes were reported every day in Uttar Pradesh, which has 200 million people and is India's most populous state.
Gupta said 60 percent of such crimes happen when women go into the fields because their homes have no toilets.
The girls in the latest incident were attacked in the tiny village of Katra, about 300km from Lucknow. They disappeared on Tuesday night after going into fields near their home to go to the toilet.
The girls were Dalits, from the community once known as "untouchables" in India's caste system.
The dismissed policemen and the men accused of the attack are Yadavs, a low-caste community that dominates that part of Uttar Pradesh. The chief minister is also a Yadav.
Official statistics say about 25,000 rapes are committed every year in India, a nation of 1.2 billion people.
Activist say that number is a percentage of the actual number, since victims are often pressed by family or police to stay quiet about sexual assaults.