The second day (Thursday) featured a series of close-door, intensive meetings, media reported on Friday. (Agencies)
EU foreign policy chief Catherine Ashton, who represented the P5+1 group - namely Britain, China, France, Russia and the US plus Germany, during the talks, met with Mohammad Javad-Zarif, head of the Iranian delegation.
The meetings were "substantial and detailed" with both sides seeking further progress, Ashton's spokesperson Michael Mann said.
A senior US official said on condition of anonymity on Wednesday evening that the focus of this round of talks is to get into details of "a possible first-step agreement and the parameters of a comprehensive agreement, and to see if we can narrow the remaining gaps necessary to conclude such an agreement".
The new round of talks which began on Wednesday is the third round of negotiations between Iran and the six major countries in more than a month.
In the last round of talks that began on November 7 and lasted for three days, the two sides failed to reach a deal.
The second day (Thursday) featured a series of close-door, intensive meetings, media reported on Friday.