Russian human rights activists have urged Moscow to hand over the body of the late Chechen separatist leader Aslan Maskhadov to his relatives.
Maskhadov's son says his father chose to "give battle and die"
Earlier, Maskhadov's children and widow asked Western leaders to put pressure on Moscow to return the body.
Maskhadov was killed last week in Chechnya, when Russian troops located a bunker where he was hiding.
The Russian authorities said Maskhadov would be buried in an unmarked grave after forensic examination.
Moscow called Maskhadov a "terrorist" and Russian law allows secret burials of people who were engaged in terrorism. However, only a court can officially declare him a "terrorist".
"We regard as shameful the refusal to return his remains to the relatives for burial," said Russian human rights activists in a statement quoted by the AFP news agency.
Former Soviet dissidents Lev Ponomaryov and Yuly Rybakov were among those who signed it.
Meanwhile, witnesses quoted by the Associated Press on Monday said the house where Maskhadov had been hiding had been blown up. The report has not been confirmed independently.
According to Moscow's version of events, Maskhadov was killed by an accidental shot after he and his bodyguards had been cornered in a bunker dug under a house in the village of Tolstoy-Yurt, 20km (12 miles) from the Chechen capital, Grozny.
But his Azerbaijan-based son, Anzor, said his father had chosen to "give battle" and died after having allowed the men who were with him to surrender.
Maskhadov masterminded the Chechen resistance for years
The independent Chechen Society electronic newspaper suggested that Maskhadov was killed not in Tolstoy-Yurt, but in another clash that took place a few days before in Nozhay-Yurt district.
The Russian Moskovsky Komsomolets newspaper even claimed that Maskhadov had been captured, "questioned and then executed".
Russian and pro-Moscow Chechen officials maintain that the authorities were interested in capturing Maskhadov alive, as he was a valuable source of information.
The Russian interior ministry says at least seven Russian soldiers were injured in a series of explosions in Grozny on Monday.
A spokesman for the troops there said the military commandant's office came under grenade attack as soldiers waited to receive their orders for the day.
The rebels vowed to step up their resistance following the killing of Maskhadov.
They chose a little-known cleric, Abdul-Khalim Saydullayev, to replace Maskhadov.