Kurukshetra, India - Hindu caste leaders in the northern Indian state of Haryana have given their backing to six people convicted last month in an "honour killing" case.
The heads of 20 caste councils also demanded legislation to ban marriages between members of the same sub-caste.
Five men were sentenced to death and one jailed for life over the 2007 murder of a young couple who married against the wishes of village elders.
Elders said they violated local customs by marrying within the same sub-caste.
'Ultimatum'
Caste leaders and protesters held a meeting in the town of Kurukshetra in Haryana state.
"We will appeal to the government to amend the Hindu Marriage Act," the Times of India website quoted Bhalle Ram, head of Bainiwal village caste council in the state, as saying.
"We are giving the Indian government an ultimatum to effect these changes," he said.
Protesters are threatening to block the road between the Indian capital, Delhi, and major cities like Chandigarh and Ambala.
They say they will appeal against the sentence handed to the six men.
Caste leaders say that by local tradition people within the same sub-caste are considered to be siblings.
The young couple - Manoj and Babli - apparently fell into this category.
They were kidnapped and killed a month after they eloped while they were travelling on a bus in Haryana in 2007. Their bodies were discovered later.
Those sentenced to death by the Haryana court last month were all relatives of the girl, Babli, and included her brother, two uncles and two cousins.
The head of the village council in Haryana's Kaithal district, which ruled against the couple's marriage, was given life imprisonment.
The case was brought to the attention of the village council by the family of Manoj, Babli's husband.
Campaigners hailed the court verdict as a blow against "honour killings", which are quite common in parts of northern India.
Correspondents say such killings have often not been reported or widely discussed in the past because families usually accept the verdicts.