The arrest of a Pakistani-American who traveled to his native country for several months before he allegedly tried to set off a bomb in Times Square over the weekend has underscored the growing prominence of Pakistan as the staging ground for attacks against the United States and other Western countries. 

Since last year, the Obama administration has been saying that Al Qaeda shifted its primary base of operations to Pakistan, and it has described the country, which has a thriving Taliban contingent of its own, as a twin front in the war in Afghanistan

While countries like Yemen and Somalia have also gained attention, the increasing number of plots out of Pakistan -- both successful and unsuccessful -- has illustrated the administration's concern. 

Authorities are looking closely at the possibility that the crudely concocted car bomb that failed to explode in the heart of New York City on Saturday was the work of international terrorists. And all signs point to Pakistan. 

-- Faisal Shahzad, the naturalized American citizen arrested and accused of planting the bomb, comes from an area near Karachi known for its connections to Al Qaeda and Lashkar-e-Taiba, the Pakistani group blamed for the 2008 Mumbai massacre. Officials say that after the suspect in the Times Square case became a citizen, he traveled to his native Pakistan -- charging documents say he admitted to recently receiving bomb-making training in the country. Pakistani intelligence sources also told Fox News that a Pakistani national was arrested Tuesday in Karachi. Sources said the suspect met last July with Shahzad in Peshawar. Others in Pakistan have since been taken into custody. 

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-- In December, five American Muslims from the Washington, D.C., area were captured and charged in Pakistan with plotting terror attacks. They were arrested in an area south of Islamabad after they disappeared, and they are accused of conspiring with Pakistani militants. 

-- In October, U.S. citizen David Headley and three others were arrested and charged with conspiring with Lashkar-e-Taiba in the Mumbai attacks and with planning an attack against the office of the Danish newspaper under fire in the Muslim world for publishing caricatures of the Prophet Muhammad. Headley, who is of Pakistani descent, pleaded guilty in March. Two of the other suspects were living in Pakistan, while the third was a Pakistani native living in Chicago with Canadian citizenship. 

-- In September, Colorado resident Najibullah Zazi was arrested and charged with plotting to bomb the New York subway system. According to the Department of Justice, Zazi, an Afghan, revealed during questioning prior to his guilty plea in February that he received his training from Al Qaeda in Pakistan. The DOJ said Zazi and others flew to Pakistan with the goal of joining the Taliban in Afghanistan, but were recruited by Al Qaeda and trained for suicide missions in the United States. 

New videotape suggests the threat from Pakistan will continue to grow. 

The leader of the Pakistani Taliban, Hakimullah Mehsud, showed up in a video Monday after U.S. and Pakistani officials had said he was killed in a January missile strike. In the video, Mehsud threatened more attacks on the United States and said Taliban operatives have "penetrated" the country. 

The Pakistani Taliban have also claimed credit for the Times Square attempt, but New York officials have questioned that claim. 

John Bolton, former U.S. ambassador to the United Nations, warned that the United States needs to continue paying close attention to what's going on inside Pakistan. 

"Pakistan is the perfect example of a country that we need to prevent falling under terrorist control. As much of a tragedy as that explosion at Times Square might have been, if Pakistan falls to the Taliban or another radical extremist group, they would be in control of Pakistan's very substantial arsenal of nuclear weapons," he told Fox News. "That's why this is so critical to understand really what the linkages might be here."