VIENNA (Reuters) - Syrian rebels who have reportedly captured a suspected nuclear reactor site - destroyed by Israel six years ago - have not been in contact with U.N. inspectors about visiting it, IAEA chief Yukiya Amano said on Monday.

The U.N.'s International Atomic Energy Agency (IAEA) has long sought access to a site in Syria's desert Deir al-Zor region that U.S. intelligence reports say was a nascent, North Korean-designed reactor geared to producing plutonium for nuclear weapons before Israel bombed it in 2007.

On February 24, opposition sources in eastern Syria said rebels had captured the destroyed site near the Euphrates River.

"Certainly we are aware of the report on (the) rebel group's offer to invite us to the site of Deir al-Zor but we are not aware of any communication to that effect," Amano, IAEA director general, told a news conference, referring to a media report last month.

The Vienna-based watchdog has also been requesting information about three other sites that may have been linked to Deir al-Zor.

Syria says Deir al-Zor was a conventional military facility but the IAEA concluded in May 2011 it was "very likely" to have been a reactor that should have been declared to its anti-proliferation inspectors.

The U.N. investigation appears to have died down since the national revolt against President Bashar al-Assad broke out in 2011, with the armed opposition increasingly capturing military sites in rural areas and on the edges of cities.

U.N. inspectors examined the site in June 2008 but Syrian authorities have barred them access since.

"I renew my call to Syria to fully cooperate with us in connection with unresolved issued related to the Deir al-Zor site and other locations," Amano earlier on Monday told the IAEA's 35-nation governing board, according to a copy of his speech.

(Reporting by Fredrik Dahl; editing by Andrew Roche)