The measure will be effective as of tomorrow.
The decision was made public by Gennadii Bukaev, an aide to Russian Prime Minister Mikhail Fradkov, during a visit to the Black Sea resort of Sochi.
"Due to the growing tensions [in Abkhazia], railway traffic between Moscow and Sukhum will stop as of 2 December 2004," Bukaev said. "The state border, including the sea border, will be reinforced."
Direct railway ties between Moscow and Sukhum had resumed in September amid protests from the Georgian government, which seeks to regain control over Abkhazia.
The Moscow-Sukhum line -- which is vital for the Abkhaz economy -- had remained idle ever since the Black Sea province won de facto independence in the mid-1990s.
Moscow helped Abkhazia secede from Georgia and has been maintaining close ties with the region, granting Russian citizenship to most of its residents and paying pensions to its elderly population.
Bukaev cited political instability in Abkhazia to justify the suspension of railway ties and the strengthening of security measures.
The Russian-Abkhaz border has been regularly closed over the past few weeks as a political crisis unfolded in the Black Sea province. The current separatist leadership is locked in a bitter dispute with its opponents.
Following the 3 October presidential ballot, Abkhazia's Central Election Commission pronounced opposition candidate Sergei Bagapsh the winner against then-Prime Minister Raul Khajimba. Both the parliament and the Council of Elders -- a traditional consultative body with no constitutional power, but with considerable authority -- have recognized Bagapsh as the new president.
But the administration of outgoing President Vladislav Ardzinba has refused to concede the defeat of Khajimba, the government's candidate. It is demanding that a new election be held, claiming that the October vote was fraudulent.
Ardzinba's claims are supported by Russia, which has threatened to impose sanctions against Abkhazia should Bagapsh proceed with plans for his inauguration, scheduled for 6 December.
On 23 November, the governor of the neighboring Russian region of Krasnodar, Aleksandr Tkachev, said he would demand that the border with Abkhazia be sealed if Bagapsh does not agree to another vote.
"If on 6 December the sides have not come to an agreement, I will personally propose that the border be closed and that [Russia] stop paying pensions to Abkhazia," Tkachev said. "Let then the Abkhaz people turn to the leaders they have illegitimately elected and ask them for money and food. Let then the Abkhaz people understand whom they chose and who is responsible for their situation."
Russia's Interfax news agency subsequently quoted an unnamed Russian government official as backing Tkachev's threats.
Bagapsh has reacted strongly to these statements, likening them to "blackmail attempts" and saying their authors are "playing into the hands of those who in Georgia dream of regaining control over Abkhazia."
But Bukaev today aired similar threats, saying the Russian-Abkhaz border will be closed if Bagapsh takes further "unconstitutional steps."
Bukaev also reiterated Moscow's support for another Abkhaz vote.
"There is a legitimate president in the republic of Abkhazia -- Vladislav Ardzinba," Bukaev said. "The Russian leadership supports his persistent efforts to stabilize the socio-political situation in the republic and his decision to hold a new election."
Officials from Russia's Interior Ministry and Prosecutor-General's Office arrived in Abkhazia on 29 November.
In the words of Deputy Prosecutor-General Vladimir Kolesnikov, who co-chairs the delegation, the aim of the visit is to "ensure that the rule of law prevails in Abkhazia." Kolesnikov also said the mission included election officials to help Abkhazia "sort out its [political] dispute."
Bagapsh, who has criticized the presence of these Russian officials in Sukhum, today told Interfax that, whatever the "pressures" exerted on him, he will go ahead with his inauguration.