A Security Awareness bulletin issued by the FBI and the Department of Homeland Security (DHS) urges vigilance over the July Fourth weekend, as terror network al Qaeda might be contemplating an attack on the Independence Day.

The annual summer holiday Security Awareness Bulletin, a six-page document, says Al Qaeda had identified July Fourth weekend of 2011 as ideal for an attack, back in February 2010. Though specific or credible information regarding a terrorist strike isn't available, al Qaeda is believed to be contemplating large scale destruction on symbolic dates.

As of February 2010, al Qaeda was contemplating large attacks in the homeland on symbolic dates and specifically identified U.S. Independence Day as a key date, the bulletin says.

We currently have no specific credible information that any plotting targeting the homeland was developed based on this reporting, and are uncertain how widely al Qaeda's interest in timing attacks for symbolic dates has been shared or accepted within the group or among its affiliates and allies, the bulletin says.

US officials reportedly connect the speculated attacks with the death of al Qaeda chief Osama Bin Laden. In an attempt to seek revenge for their leader's death, the terror network members might strategically choose dates of national significance, increasing the symbolic effect of attacks, administrative officials believe.

Large gatherings, such as the congregation to enjoy New York City's annual fireworks display, make especially attractive targets during the holiday season, the bulletin says. Such targets offer the opportunity to inflict mass casualties, with the added objectives of causing economic and psychological damage on the United States.

The bulletin also says al Qaeda always had aspirations of executing a high profile attack inside the US, with lesser importance to when it occurs.

Previous examples of this desire (executing a high profile attack) include the May 2010 attempted detonation of a vehicle-borne improvised explosive device in Times Square, the guilty plea in February 2010 to an al Qaeda plot to attack the New York City subway using improvised explosive devices, and al Qaeda in the Arabian Peninsula's inclusion of photos of and references to major U.S. cities in their Inspire magazine, the report says.

The bulletin covers the season from Memorial Day weekend through Labor Day and is intended to create awareness among public and private sector partners in the security and counterterrorism sectors.