Several dozen people greeted Foreign Minister Mohammad Javad Zarif and his team as they left Tehran's Mehrabad airport after returning from the negotiations in Lausanne, the ISNA news agency reported.
"Viva Zarif! Viva Araghchi!" the crowd chanted, in reference to the minister and one of the main negotiators, Abbas Araghchi.
In brief remarks at the airport, Zarif praised Iran's supreme leader Ayatollah Ali Khamenei for "his remarkable support for the negotiating team and his guidance" in the talks, the official IRNA news agency reported.
Reaching out to Iranian hardliners who have opposed any deal that would curb Tehran's nuclear activities, Zarif said work remained to finalise the agreement before a June 30 deadline.
"This set of solutions will be the basis for writing a final document," he said in the airport.
"In negotiations, it is not supposed to be one side taking all the advantages and the other side surrendering," Zarif said.
"We are proud because we will never surrender... but in return for the advantages that we gain, we will give things in return so we can move on," he said.
"We have serious goals in the negotiations and eventually, based on what we have achieved so far, we believe we can reach them," he added.
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Residents lined the streets as Zarif drove away from the airport, some carrying Iranian flags, with the minister emerging from the sunroof of his car and waving to the crowd.
Ali Akbar Salehi, who led the technical negotiations in Lausanne, said the outline agreement was a major step forward.
"We will move on," Salehi said on arrival in Tehran. "We are on the launching pad -- in international relations, technology, trade and the economy."
In the wake of Thursday's agreement, several conservative websites published comments from Mehdi Mohammadi, a political analyst, describing the deal as "in no way balanced".
He said the agreement was a "disaster for Fordo", referring to a nuclear facility that will remain open but not used for enrichment.
He also said the deal was "vague on the timing of sanctions relief".
Saeidollah Allahbedashti, an aide to President Hassan Rouhani, denounced claims that he said were undermining the achievements of negotiators.
"The public has proven it can understand the difference between traitors and those who serve" their country, he said at the airport.