VIENNA (REUTERS) - The UN's nuclear watchdog said it had a "constructive exchange" with Iran on two issues related to Teheran's nuclear programme which the agency has tried to clarify but which Iran has been stonewalling since August.

The International Atomic Energy Agency (IAEA), which held technical talks with Iranian officials in Teheran on Wednesday, said on Thursday the two sides would meet again soon, without giving a date.

The IAEA investigation runs parallel to talks between Teheran and six world powers that aim to broker a deal by end-June to scale down Iran's nuclear programme in exchange for sanctions relief.