Islamabad, Pakistan (CNN) -- Relatives of a 21-year-old Pakistani woman are under arrest for allegedly electrocuting her because she secretly married a man they didn't approve of, police told CNN.
Police arrested Saima Bibi's father and three other relatives after being tipped off by an anonymous caller, said police official Muhammad Ismail.
Bibi -- an ethnic Baluch -- defied demands from her family to marry a Baluch relative and instead ran away about one month ago to the southern port city of Karachi to marry a fellow villager, police official Rao Zahoor said.
Her father and several other relatives traveled to Karachi and duped her into coming back home. When she didn't listen to further demands they electrocuted her, he said.
Bibi's family told police she committed suicide on Friday in their village in the district of Bahawalpur in Punjab, but a medical report showed signs of torture and electrocution on her hands, legs and back, police said.
Human rights groups say so-called honor killings -- the murder of women accused of infidelity and dishonorable behavior -- are a growing problem in parts of Pakistan.
A 2009 study by the European Journal of Public Health showed one out of every five homicides in Pakistan was an honor killing.
Some Baluch communities in Baluchistan province and parts of Sindh and Punjab provinces still justify honor killings.
The government is doing little to stop the killings, said Iqbal Haider, the head of the Human Rights Commission of Pakistan.
"Sindh and southern Punjab are where the situation of honor killings is the worst. It's an absolute menace," Haider told CNN. "The government is doing nothing at all. Beyond lip service they have done nothing. It's just careless indifference."
Journalist Nosheen Abbas contributed to this report.