"Under the NPT, the agency has a responsibility to verify any proliferation allegations in a non-nuclear weapon state party to the NPT," the agency said.
North Korean help ElBaradei also said the agency would investigate the claims that Syria was building a secret nuclear reactor with North Korea's help.
Washington alleged that the facility had a military purpose until Israel destroyed it in a bombing raid last September.
The watchdog was critical of both the US and Israel for their handling of the matter.
"In light of the above, the director-general views the unilateral military action by Israel as undermining the due process of verification that is at the heart of the non-proliferation regime," it added.
The agency said it was taking seriously the allegations that were passed on by the United States on Thursday and will investigate the findings.
"[We] will treat this information with the seriousness it deserves and will investigate the veracity of the information," it said.
"Syria has an obligation under its safeguards agreement with the IAEA to report the planning and construction of any nuclear facility."
The White House said in a statement on Thursday that Syria "must come clean" over its alleged secret co-operation with North Korea on the reactor.
It also described the alleged assistance as a "dangerous manifestation'' of North Korea's nuclear proliferation activities, but said it would continue six-party talks to try to resolve the nuclear standoff with the isolated nation.
The claims follow a briefing of US congressional officials in Washington DC by intelligence chiefs, including William Hayden, the CIA director.
However, some US legislators earlier warned that the claims could wreck vital six-party talks on North Korea's nuclear programme.
Later on Thursday, Syria's ambassador to the US dismissed claim as a "ridiculous story".
Imad Moustapha told Al Jazeera that his government maintained there was no evidence of any alleged secret nuclear activity.
Timothy Savage, an analyst from the Nautilus Institute, told Al Jazeera that the US claims could be treated with a degree of sceptism.
"The Bush administration doesn't have a great track record with intelligence, so it's natural that people will approach this with some scepticism," he said.
'Nuclear facility'
The controversy began last September, when an Israeli air raid destroyed a target in Syrian territory which some reports later said was a nuclear facility being built with North Korean help.
Syria, a signatory to the nuclear Non-Proliferation Treaty (NPT), has maintained in the past that the site was an unused military facility.
It later razed the site and built a larger building in its place.
The target of Israel's raid has been veiled in secrecy, with US intelligence and government officials refusing to confirm for months that such a raid even took place.