Osama bin Laden has been killed, but the hunt is still on for remaining leaders of al-Qaida and the other terrorist groups who continue to pose a threat to Americans.
Bin Laden appeared at the top of both the FBI's list of the 30 most wanted terrorists and its list of 10 most wanted fugitives. He became Public Enemy No. 1 after the terrorist attacks of Sept. 11, 2001, which he masterminded.
"No one can replace bin Laden in stature and cult-like status and name recognition. It's unlikely that's going to happen," said Rick Nelson, director of the homeland security and counterterrorism program at the Center for Strategic & International Studies.
Still, there are many suspected terrorists who are key to al-Qaida and other anti-American organizations, and who could prove extremely dangerous to the United States and its citizens. Some experts say that the death of bin Laden could spur reprisal attacks from his followers.
"The terrorists almost certainly will attempt to avenge him, and we must - and will - remain vigilant and resolute," Leon Pannetta, the director of the Central Intelligence Agency, said in a statement Monday.
Here is a look at some of the remaining terrorists still at large:
Ayman al-Zawahiri: The Egyptian-born al-Zawahiri has long been bin Laden's No. 2 man, and he remains a key target for law enforcement officials. There is a $25 million reward for information leading the FBI to al-Zawahiri, who is believed to have played a key role in the 1998 bombings of U.S. embassies in Dar es Salaam, Tanzania and Kenya.
Anwar al-Awlaki: An influential leader with al-Qaida in Yemen,al-Awlaki is considered especially dangerous in part because he was born in New Mexico and is a U.S. citizen of Yemeni descent, Nelson said. He's also considered extremely effective at recruiting.
Adnan el Shukrijumah: Thought to be a senior al-Qaida leader in its external operations program, the FBI also has linked el Shukrijumah to a plot against the New York subway system that was uncovered in late 2009. There is a $5 million reward for information leading to his capture.
Mullah Omar: NBC investigative producer Robert Windrem places him high on the list of counterterrorism priorities because of his leadership role with the Taliban and because he sheltered bin Laden prior to the Sept. 11 attacks.
Adam Yahiye Gadahn: Gadahn also is considered particularly threatening because he's an American who has been outspoken against the United States, Nelson said. The FBI, which offers a reward of up to $1 million for information leading to his capture, alleges that he has been involved in a number of al-Qaida terrorist activities.
Omar Hammami: Hammami is believed to be a key figure in the Shabab movement in Somalia. In a profile last year, The New York Times dubbed him "The Jihadist Next Door" because of his unlikely journey from a childhood in Alabama to a key post in an Islamist guerrilla army.
Saif Al-Adel: Al-Adel also is wanted in connection with the 1998 embassy bombings, and the FBI is offering a reward of up to $5 million for his capture. The FBI says he is believed to be a high-ranking al-Qaida member, and BBC News reported that al-Adel was once Bin Laden's security chief.
