Two more Tibetans have died in separate self-immolations, and the Dalai Lama has accused China's government of not seriously investigating the incidents.
According to Chinese state media, the total number of people to have set themselves on fire since the China's Communist Party opened its sensitive congress last week has risen to nine.
The latest incidents took place in Tongren on Monday, a county in northwest China's Qinghai province, Xinhua news agency said.
AFP quotes the UK-based Free Tibet group as saying that one of the protesters was a man in his mid-20s called Nyingkar Tashi who set himself alight during a prayer ceremony for a young mother who self-immolated in the area earlier this month.
He reportedly called out for freedom in Tibet and for the long life of the Dalai Lama.
The number of self-immolations protesting against Chinese rule of the Tibetan heartland have escalated since 2009.
The India-based Tibetan government-in-exile had counted 69 incidents, of which 54 resulted in death, before the latest incidents.
Dalai Lama reacts
Meanwhile, the Dalai Lama has said China's government is not "seriously" probing the cause of a spate of self-immolations by Tibetans.
Tibet's spiritual leader-in-exile made the comments to reporters in Okinawa, Japan, on the last leg of a 12-day visit to the country.
"The Chinese government should investigate the cause (of the incidents)," he said.
"China does not look into it seriously and tries to end (the incidents) only by criticising me."
The Dalai Lama's comments are thought to be the first on the issue since the Congress began in Beijing last week.
On the sidelines of the congress on Friday, officials from the Tibetan Communist Party angrily denounced the Dalai Lama and overseas Tibetan "separatists" for orchestrating the immolations to breed unrest.
"The Dalai Lama clique and overseas Tibetan separatists have been sacrificing other people's lives for their own secret political aims," Losang Gyaltsen, vice-chairman of the Tibet region's government said.