Islamist groups around the world have hailed the Taliban's takeover in Afghanistan, sparking global alarm that the country could once again become a safe haven for jihadis inspired by its success.

The Taliban has said it will not allow Afghanistan to be used to launch attacks on other nations. But experts say that ties remain with al-Qaida, whose attacks against the United States prompted Washington to invade the country in 2001, as well as other militant groups including in neighboring Pakistan.

One of the Taliban's top leaders is Sirajuddin Haqqani, the head of the militant Haqqani network. The U.S. has designated him a global terrorist and offered $5 million for information leading to his arrest.