UN inspectors have returned from a trip to Syria and are now analysing the data they collected there, the International Atomic Energy Agency said Monday.

"IAEA inspectors have returned from Syria and will now analyse the information they have collected," a spokesman for the Vienna-based watchdog said.

After stonewalling an IAEA probe for more than two years, Damascus finally gave nuclear inspectors permission earlier this year to fly to Syria on April 1 to visit a site at Homs.

The IAEA has been investigating allegations since 2008 that Syria had been building an undeclared reactor at a remote desert site called Dair Alzour until it was bombed by Israeli planes in September 2007.

Damascus granted UN inspectors one-off access to that site back in June 2008 but has not allowed any follow-up visits to either Dair Alzour or other possible related sites since then.

Homs, north of Damascus, is not one of the suspect sites, but the IAEA welcomed Syria's decision to allow the visit, seeing it as a possible first step forward in its hitherto stymied investigation.