An energy ministry spokesman in Moscow made the announcement on Tuesday.
"I can only tell you one thing, that they have been freed," said Yury Nogotkov, a spokesman for the Industry and Energy Ministry. "I cannot provide any other details."
The detained men were released after their abductors learned
they were from Russia, RIA Novosti news agency quoted an unnamed Interenergoservis employee in Baghdad as saying.
Earlier, foreign ministry spokesman Alexander Yakovenko said the eight were employees of the Interenergoservis company in Baghdad.
Russia vehemently opposed Washington's war against Iraq last year.
The abductors apologised to the detainees and put them into a taxi, RIA reported.
The kidnapped men were handling repairs at a thermo-electric
power station in the Iraqi capital.
They were kidnapped on Monday when 15 to 20 masked men burst into a house where they were living in northeast Baghdad, Russian news agencies reported.
Late on Monday Aljazeera television's Moscow correspondent reported that 11 Russians had been seized after a shootout between their Iraqi guards and abductors.
Two Iraqi guards might have been killed in the clashes, an official from the energy company said.
Russia has refused to contribute any ground forces to the occupation and has about 600 specialists working in Iraq, mainly in the oil sector.
Interfax news agency reported that Moscow's biggest contractor in Iraq is evacuating all 370 staff.
New Zealand Prime Minister Helen Clark said army engineers in Iraq might also be evacuated if the unrest continued. The engineers have been confined to their quarters at a former naval academy near the southern city of Basra for days.
The latest kidnappings coincide with the release of seven Chinese men on Monday after the Association of Muslim Scholars (AMS), the highest Sunni authority in Iraq, called for their freedom, reported Aljazeera.
The Chinese men were released a
day after their capture
Masked men handed them to AMS officials at a Baghdad mosque a day after they were captured. They were later handed to Chinese diplomats in Baghdad.
Their captors left a letter saying they belonged to a group called Abu Ubaida al-Jarrah Brigade.
Representatives of the AMS later handed the hostages to the First Secretary of the Chinese Embassy in Baghdad.
The men were captured on Sunday in the city of Falluja after entering Iraq from Jordan.
The men are said to be in good spirits and some of them want to forge ahead with plans to open a construction business there despite their ordeal, said Chinese officials.
Chinese security sources told Aljazeera the hostages went to Iraq at their own risk.
Another eight hostages, mainly truck drivers and labourers, from Pakistan, Turkey, India, Nepal and the Philippines were released on Sunday. A British contractor was also released after local tribal leaders urged the captors to release him.
Fate of Japanese
Despite the release of the hostages, Japanese Prime Minister Junichiro Koizumi warned his Cabinet on Tuesday not to get too optimistic and said Tokyo had yet to confirm that three Japanese who remained in captivity were safe.
A protester carries a picture of
three Japanese hostages in Iraq
And Japan's defence minister on Tuesday cancelled plans to visit Japanese troops in southern Iraq due to security concerns, Kyodo news agency said on Tuesday.
Defence Minister Shigeru Ishiba had planned to visit Iraq
around Tuesday to boost the morale of the approximately 550
troops in the southern city of Samawa, according to the media report.
A defence ministry spokesman could not comment on the report, which said the plan was scrapped because of unrest among followers of Shia leader Muqtada al-Sadr in parts of southern Iraq.
With its hostage crisis dragging into a sixth day, Japan's government scrambled to glean information on the condition of the freelance photojournalist and two aid workers - one just 18-years-old.
Hopes for the freedom of the three, among more than two dozen people from 12 countries, kidnapped in recent days in Iraq, were bolstered by the release of the Chinese.
But officials and families of the Japanese hostages struggled to hide their frustration with the lack of news on the fate of the captives. The hostages are Noriaki Imai, 18, Soichiro Koriyama, 32, and Nahoko Tokato, 34.
Last Thursday, Aljazeera aired a videotape showing the Japanese civilians seated at the feet of their heavily armed captors, named as members of a previously unknown group called Saraya al-Mujadadin.
The group demanded Tokyo should withdraw its troops from Iraq.
Chief Cabinet Secretary Yasuo Fukuda has admitted the government has little to go on and no confirmation that the captives are safe.
Fukuda said Koizumi warned his cabinet against optimism.
Tokyo's controversial deployment of 1100 troops is the country’s riskiest overseas military mission since the second world war.
Families of the Japanese
hostages call for a troop pullout
Critics say the deployment violates Tokyo’s pacifist constitution.
Despite pleas from the hostages' families, Koizumi has vowed not to withdraw troops.
The fate of aid workers Fadi Ihsan Fadal, a Syrian-born Canadian from Montreal, and Palestinian Nabil George Yaqub is still unclear. They were also kidnapped last week.
More foreigners missing
Separately, another seven US contractors working for Halliburton subsidiary Kellog, Brown and Root were reported missing on Monday. Another two Czech state television journalists and one radio correspondent are missing and may have been kidnapped, reported the public broadcasters on Monday.
Martin Krafl, spokesman for Czech Television, said cameraman Petr Klima and reporter Martin Kubal had hired a car and driver to take them from Baghdad to neighbouring Jordan on Sunday morning.
Krafl said the two were last seen on Sunday morning, but gave no further details.
State radio reporter Vit Pohanka, who was also due to make a trip from Baghdad to Amman, is unaccounted for, said the local CTK news agency, quoting Czech Radio's Foreign Editor Jiri Hosek.
Despite the hostage crises, Australian Prime Minister John Howard said on Tuesday he would not order Australian civilians working in Iraq to leave the country.
"Everybody is at some degree of risk and we are in contact through our office as best we can with the 60 to 80 Australian contractors who are doing different things there," said Howard. "I am not asking them to get out."
Canberra was one of Washington's staunchest allies in the war on Iraq. Howard has said the 850 Australian troops in and around Iraq will stay as long as they are needed, despite calls from the public to withdraw them.