The statement signed by bin Laden and dated Sunday did not address allegations that he masterminded the Sept. 11 attacks on New York and Washington, but he has denied involvement on two earlier occasions.
"I announce to you, our beloved brothers, that we are steadfast on the path of jihad (holy war) with the heroic, faithful Afghan people, under the leadership of Mullah Mohammed Omar," said the statement, which Qatar's Al-Jazeera satellite channel said it received Monday.
Omar is the leader of Afghanistan's ruling Taliban militia, which has harbored bin Laden since 1996 and has refused U.S. demands to turn over the Saudi exile and his lieutenants to the United States, among other things, or face attack. The United States has been building up its military presence in the region since the attacks.
Bin Laden, believed in hiding in Afghanistan, often communicates with the outside world through Al- Jazeera, known among Arabs for its wide reach and its independent and aggressive editorial policies.
In the statement broadcast Monday by Al-Jazeera, bin Laden said he was informed that some "of our Muslim brothers in Karachi (Pakistan) were killed while expressing their opposition to the aggression of the American crusade forces and their allies on Muslim lands in Pakistan and Afghanistan."
He said he was praying to God that they would be accepted as martyrs, and "their children are my children and I will be their caretaker."
"We hope that they are the first martyrs in Islam's battle in this era against the new crusade and Jewish campaign led by the big crusader Bush under the flag of the cross."
It was a reference to the Crusades, the medieval wars against Muslims in the Holy Land waged by Christian monarchs. Bush recently used the word to describe his promised campaign against terrorism, stoking suspicion among some Arabs and Muslims that he was singling them out. A White House spokesman later said Bush meant to refer to a "broad cause" against terrorism, but regretted using the word.
Demonstrations have been held in the Pakistani cities of Karachi, Peshawar and Quetta by Pakistanis who view bin Laden as an Islamic hero and object to their government's decision to cooperate with the United States in its anti-terrorism campaign.
Bin Laden said that he was calling on all Muslims in Pakistan to use all they possess and all their effort to stop American troops from going into Pakistan and neighboring Afghanistan.
The United States has said it will produce evidence implicating him in the Sept. 11 attacks, which toppled the World Trade Center towers and part of the Pentagon and left more than 6,000 people dead or missing.
The Taliban claimed Sunday they have been unable to find the alleged terrorist mastermind and advise him of a recommendation by their Muslim clergy to leave the country. But U.S. officials say they believe the Taliban know exactly where he is.