Iran and the UN atomic watchdog, following a day of discussions on the Islamic republic's controversial nuclear programme, agreed on Thursday to resume negotiations in Tehran on January 16 , a senior Iranian official said.

"We agreed to have the next round of talks on January 16 in Tehran," said Ali Asghar Soltanieh, Iran's representative to the International Atomic Energy Agency was quoted by media as saying.

The one day of talks held on Thursday was "constructive, positive, and good progress has been made," he added.

No other information came out of the talks, which ran from the morning late into the evening.

The agency wants to inspect Parchin, a restricted military complex near Tehran where the IAEA suspects experiments with explosives capable of triggering a nuclear weapon could have been carried out.

But the media did not say whether that request was granted.

In Vienna, the IAEA had no comment, but chief inspector Herman Nackaerts, who was leading the seven-strong team, was expected to make a statement on his return there on Friday morning.

The IAEA says the talks aim to reach agreement on a "structured approach" for Tehran to address allegations of weaponisation and for the watchdog to gain broader access to Iran's nuclear sites and people working in the programme.

"We also hope that Iran will allow us to go to the site of Parchin, and if Iran would grant us access we would welcome that chance and we are ready to go," Nackaerts told reporters in Vienna on Wednesday before leaving for Iran.

The IAEA, which visited Parchin twice in 2005, accuses Tehran of carrying out clean-up operations at the base to undermine its efforts to probe possible past nuclear weapons research work. Iran denies that.

Thursday's talks were the latest in a string of fruitless meetings this year between Iran and the IAEA, with the latest in August in the Austrian capital.

One diplomat in Vienna said the team in Tehran is larger than in past visits in February and in May, and now included two "technical experts" who could conduct verification work at Parchin -- if invited to do so.

Iran denies seeking or ever having sought an atomic bomb and has refused the IAEA access to Parchin, saying that as a non-nuclear site the agency has no right to conduct inspections there.

Foreign ministry spokesman Ramin Mehmanparast said on Tuesday the visit would focus on discussions regarding "Iran's nuclear rights as well as its peaceful nuclear activities."

But "certain issues that have possibly become a source of concern for (IAEA) officials can also be discussed," he said, without being more specific.

Iran, under international sanctions, rejects as baseless suspicions by Western governments and echoed by the IAEA that it intends to develop a nuclear weapons capability under the guise of its energy programme.

It stresses that IAEA demands to examine Parchin exceed Iran's obligations under the Nuclear Non-Proliferation Treaty (NPT), to which it is a signatory.

The inspectors' visit also came against the backdrop of renewed efforts by world powers engaging Iran over its nuclear programme to discuss possible dates and venues for a new meeting to resolve the dispute.

The P5 + 1 -- the US, Russia, China, France and Britain plus Germany -- are hoping to agree with Iran "rapidly" on a new meeting, a spokesman for EU foreign policy chief Catherine Ashton said in Brussels.