Human rights groups decried the deal while China kept a low profile, not confirming Tuesday's announcement by Guinea, a West African country led by Capt. Moussa "Dadis" Camara who seized power in a coup in December.
"There's a real risk that these investments could entrench and embolden and enrich an already abusive government," said Arvind Ganesan, director of Human Rights Watch's Business and Human Rights Program.
Chris Alden, an international policy expert at the London School of Economics, said Camara "apparently pulled the rabbit out of the hat for this regime."
"We're talking about a desperate captain who ran a coup, who's actively being delegitimized," Alden noted.
The deal gives Guinea's military junta a major potential source of revenue even as it faces isolation from the international community after soldiers opened fire on Sept. 28 at demonstrators opposed to Camara running in elections planned for January.
A local human rights group said 157 protesters died while the government put the death toll at 57. Witnesses say soldiers also raped women in the streets.
Guinea announced the agreement on Tuesday, a national day of mourning for those killed by the troops at Guinea's national stadium.
The United States has called for Camara to step down, while former colonial power France has said it can no longer work with him. The African Union already had suspended Guinea's membership following the coup.
Ganesan said the mining deal's timing is "unfortunate."
"It certainly sends the wrong message at the wrong time," the rights advocate said. "After widespread abuses have taken place in Guinea, for the government to be able to tout a $7 billion deal with the China International Fund says that they are above criticism."
Guinea is the world's largest producer of bauxite, the raw material used to make aluminum, and produces diamonds and gold. Mines Minister Mahmoud Thiam said Tuesday that the Chinese company "will be a strategic partner in all mining projects."
U.S. State Department spokesman P.J. Crowley would not comment directly on this specific business deal, but noted the U.S. has "expressed concerns about this kind of activity. We think it's important that as you do business with countries you also have respect for human rights."
David Shinn, a former U.S. ambassador to Ethiopia and Burkina Faso and an expert on Chinese-African relations, said the timing of the announcement was strategic on Guinea's part.
"The fact that the announcement came from Guinea and not Hong Kong or China is important," he said. "I can't imagine that China would want to use this timing to announce it."
Africa's trade with China reached more than $100 billion in 2008 and has multiplied by 10 since 2001, according to the African Economic Outlook. China's policy of operating on purely business terms has raised questions about whether it will hamper the progress of human rights in Africa.
China is accused of protecting the government of Sudan, its oil supplier, despite the conflict in Darfur that has claimed at least 300,000 lives from violence, disease and displacement. The Chinese also helped construct a private palace for Zimbabwean President Robert Mugabe, who is ostracized by Western governments that accuse him of ruining his nation's economy and stifling democracy.
"The Chinese have never had any concerns about working out deals with non-democratic governments," Shinn said. "And for that matter, some Western countries and their corporations haven't either."
Despite Guinea's mineral wealth, the country remains one of the world's poorest. Its soil had been plundered by two consecutive dictatorships before Cmara seized control of the country a day after President Lansana Conte, who had ruled for nearly a quarter-century, died Dec. 22.
After seizing power, Camara vowed to renegotiate the country's numerous mining contracts, saying the country's ruling elite had "spit on the faces of the poor" and enriched themselves at the population's expense.
Camara initially was embraced by Guineans, but tensions have risen amid rumors that he may run in presidential elections scheduled for Jan. 31. He initially indicated that he would not but said recently he has the right to do so if he chooses.
Associated Press writers Carley Petesch in Johannesburg and Robert Burns in Washington contributed to this report.