Moscow (AFP) - Russia on Friday announced a proposal to finally bury the remains of Tsar Nicholas II's son and heir Alexei and daughter Maria alongside their family in Saint Petersburg next month.

But a government spokeswoman cautioned the plan had not been given final approval, amid objections from the Russian Orthodox Church.

A high-level government task force put forward a proposal for the burial to take place in Russia's former imperial capital on October 18.

The task force "will propose to the government the holding of a burial ceremony of the remains of Tsarevich Alexei and Grand Duchess Maria on October 18," it said after meeting on Friday.

But Prime Minister Dmitry Medvedev's spokeswoman, Natalia Timakova, later told RIA Novosti state news agency "there has not been a final decision on the date."

She said that further consultations would be held, including with the Russian Orthodox Church.

The task force proposed that the burial take place in the former imperial capital's Peter and Paul Cathedral, where Nicholas II, his wife and their three other children were buried in 1998.

"The Saint Petersburg authorities have drawn up the ceremony for all the events linked to the burial," Saint Petersburg's deputy governor Vladimir Kirillov told Interfax news agency.

- 'Believers have many questions' -

But the powerful Orthodox Church, which has long delayed the funerals over doubts about the victims' identity, called for additional testing of the remains.

The Church says it still has concerns about the remains based on historical records and will not recognise them if there is any doubt. It does not acknowledge the remains of any of the tsar's family.

"It is very important that all possible new tests are carried out," Church spokesman Vsevolod Chaplin told Russian news agencies, saying "believers have many questions."

The Orthodox Church has canonised all the Romanov family, who were executed by the Bolsheviks, as martyrs.

It has so far refused to acknowledge the results of DNA identity tests by Russian criminal investigators.

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The task force said that on the Church's request it asked investigators, forensic experts and geneticists to submit proposals for additional testing "if it were necessary to resolve any historical problems."

The remains suspected to be Alexei and Maria were found in 2007, 70 kilometres (43 miles) from those of their parents and sisters. Alexei, who suffered from haemophilia, was 13 when he was murdered, while Maria was 19.

The remains have been stored in a repository, the State Archives, since their discovery.

"I believe it has been absolutely firmly, definitely, scientifically and reliably proven that these remains are those of Alexei and Maria," the head of the State Archives, Sergei Mironenko, who is a member of the government task force, said in televised comments.

A descendant, Prince Dmitry Romanov, called the plan to finally bury the last tsar's children a "huge relief."

"Finally the heir and the tsar's daughter Maria can be buried together with their sisters and parents," he said in comments to TASS state news agency.

The tsar's family and their servants were shot and thrown into a mineshaft in 1918 before being burnt and hastily buried.

The remains of Nicholas II, his wife and their daughters, 22-year-old Olga, 21-year-old Tatiana and 17-year-old Anastasia were found in 1991.

Russia set up a task force in July in a fresh drive to resolve the dispute over the remains, led by the head of the government's administration, Sergei Prikhodko.