PARIS — The top Iranian atomic energy official was quoted Wednesday as saying that his country had begun to install more sophisticated enrichment devices at its Natanz nuclear site. The development coincided with the start of a new round of talks with negotiators from the UN nuclear watchdog.

Fereydoon Abbasi, the head of Iran’s Atomic Energy Agency, said scientists began putting in the new centrifuges last month, according to the semiofficial Iranian Students’ News Agency.