Pakistani officials have reiterated their determination to fight Islamic extremism inside their country following the release of an audio message from al-Qaida leader Osama bin Laden. The message appears on Islamic militant Web sites and threatens a holy war against authorities in Islamabad.

In the tape, bin Laden urges his followers to retaliate for the Pakistan Army's raid on the Red Mosque in Islamabad in July. Correspondent Simon Marks reports from Pakistan.

A recent al-Qaida message urges retaliation against the government of Pakistan

The speaker chides President Pervez Musharraf for ordering the attack on the Red Mosque to flush out Islamic militants  and the killing of more than 100 people.

Bullet holes in the trees surrounding the rubble of the compound testify to the violence of the standoff.  It left President Musharraf vowing to come to grips with Islamic militants who have been responsible for a string of increasingly bold attacks in Pakistan.

"Extremism and terrorism have not yet ended in Pakistan. This should be clear to us. But it is our resolve that extremism and terrorism -- wherever it is in the country -- we have to eliminate it," said the president.

The Pakistani government says its battle against extremism has public support. The vast majority of people in Pakistan follow a moderate, peaceful form of Islam. Sufi shrines across the country are busy places where worshippers follow a mystic form of the faith.

But extremist attacks -- including one two weeks ago in Rawalpindi -- do have a network of supporters in Pakistan. The U.S. government's National Intelligence Estimate recently concluded that al-Qaida is regrouping in Pakistan.

And there are some Islamic voices in the country that express views deeply hostile to the Pakstani government and its contributions to the U.S.-led fight against terrorism.

Syed Munawar Hasan is the secretary general of Jamaat-e-Islami, one of the country's largest Islamic political parties. "They [Americans] are supporting Pervez Musharraf, they are opposing the people of Pakistan. American policies are always anti-Muslim, anti-Islam and anti-people, throughout the world, all over the globe. So that is what they are doing here also."

Jamaat-e-Islami operates from a 16-hectare compound in the city of Lahore that was once a movie studio. It is vowing to change Pakistani society through the ballot box. It already controls the government in one Pakistani province, is in coalition in a second and favors the introduction of strict sharia law.

Its leaders say they do not condone acts of violence. But in the party's gift shop, DVDs extolling acts of violent jihad are on-sale alongside children's cartoons.

And it is the young people of Pakistan that analysts say are especially susceptible to a radical Islamic message. With the public education system underfunded, religious schools, or madrasas, are now schooling an estimated one-and-a-half million Pakistani children. They get free food, shelter and clothing, and learn the Koran by rote.

Observers, such as retired Pakistani Lieutenant General Talat Masood, say the rise of radical Islam is a worrisome trend for the country. "It is growing. And one has to take several measures in order to countervail it. And if these are not done, then I'm certain that it will expand and it will engulf Pakistan."

Pakistani officials say the nation is behind the army's campaign to combat extremism. But the new threat by Osama bin Laden only underscores the fact that Pakistan is now a front-line state in the battle with radical Islamic ideology.