Washington, Aug 6 (IANS): The US decision to close its diplomatic missions and issue a worldwide travel alert resulted from intercepted communications from Al Qaeda leader Ayman al-Zawahri, a media report said.

According to a report on the New York Times' website Monday, the intercepted conversations last week were between Ayman al-Zawahri and Nasser Wuhayshi, the head of the Yemen-based Al Qaeda in the Arabian Peninsula, and they revealed one of the most serious plots against the US and other western interests since the World Trade Center attacks Sep 11, 2001, Xinhua reported.

The report quoted intelligence officials and lawmakers.

Zawahiri was reported to have ordered Wuhayshi to carry out an attack as early as last week, but the intercepts did not reveal the specific location or target of the attacks.

The report said it is highly unusual for senior Al Qaeda leaders in Pakistan to discuss operational matters with the group's affiliates, so when the intercepts between the two senior Al Qaeda leaders were collected and analysed, they were taken seriously, and members of Congress were quickly provided briefings on the matter.

The US last week announced the closure of its 19 diplomatic missions in the Middle East and Africa to cope with potential terrorist attacks against western interests.