"The Government of Sri Lanka is highly disturbed with regard to the statement made by the Norwegian facilitator, as the government neither agreed for unconditional talks nor was consulted," the government said in a statement on Wednesday.
Keheliya Rambukwella, Sri Lanka's defence spokesman, said he was "surprised" when Erik Solheim, Norway's international development minister, announced on Tuesday that the two sides had agreed to talks without any conditions.
Solheim told a meeting of the country's aid donors that negotiations could begin in the first week of October in Oslo, the Norwegian capital.
"The government of Sri Lanka said it was ready for talks without any pre-conditions and the LTTE [Tamil Tiger group] has said the same," Solheim told the AFP news agency.
Rambukwella accused Solheim of misleading the international community and the public.
"To the surprise of the government, Mr Solheim is reported to have announced that the talks would take place in Oslo," Rambukwella said in a statement. "... the government neither agreed to unconditional talks nor was consulted."
"The government neither agreed to unconditional talks nor was consulted".
Sri Lanka's defence spokesman
However, the government's "Peace Secretariat", which coordinates with Norway, published a statement on its website from the United States, Japan, European Union and Norway welcoming the talks.
"The Co-Chairs welcome the expression of willingness of the government of Sri Lanka and the LTTE to come to talks unconditionally as conveyed to the Facilitator," the statement said.
Solheim's announcement followed an invitation for Mahinda Rajapakse, the Sri Lankan president, to the Liberation Tigers of Tamil Eelam (LTTE) to enter talks.
The government has said it is committed to holding talks with the Tigers as long as they agree to "a comprehensive and verifiable cessation of hostilities".
The Tamil Tigers pulled out of peace talks indefinitely in April and heavy fighting resumed in late July leaving hundreds of people dead.
The Tigers want an independent homeland for minority Tamils in the north and east of the island, saying they are discriminated against by the majority Sinhalese, who dominate the government and the army. The government has ruled out anything more than local autonomy.
The army has captured LTTE territory near the port of Trincomalee and says it has overrun Tiger frontline positions in the Jaffna peninsula in the far north.
An explosion in a chicken market in the northern town of Vavuniya on Wednesday wounded 16 civilians, police and witnesses said. Police also said that they believed the Tigers exploded a grenade inside the market.
Both sides have accused each other of trying to restart the civil war which has killed more than 65,000 people since 1983 and forced hundreds of thousands to flee their homes.