KABUL, Afghanistan (AP) – International peacekeepers clashed Tuesday with Afghans protesting drawings of the Prophet Muhammad, leaving three demonstrators dead and prompting NATO to send reinforcements to a remote northern city.

Senior Afghan officials said al-Qaida and the Taliban could be exploiting anger over the cartoons to incite violence, which spread to at least six cities in a second day of bloody unrest in Afghanistan.

Demonstrations rumbled on around the Muslim world, and the political repercussions deepened, with Iran suspending all trade and economic ties with Denmark, where the drawings were first published. The Danish prime minister called the protests a global crisis and appealed for calm.

In a new turn, a prominent Iranian newspaper, Hamshahri, invited artists to enter a Holocaust cartoon competition, saying it wanted to see if freedom of expression _ the banner under which many Western publications reprinted the prophet drawings _ also applied to Holocaust images.

The drawings _ including one depicting the prophet wearing a turban shaped as a bomb _ have touched a raw nerve among Muslims. Islam is interpreted to forbid any illustrations of Muhammad for fear they could lead to idolatry.

Violence has escalated sharply in Afghanistan this week, and seven people have died in demonstrations during the past two days. Protests, sometimes involving armed men, have been directed at foreign and Afghan government targets _ fueling suspicions there’s more behind the unrest than religious sensitivities.

“It’s an incredibly emotive issue. This is something that really upset Afghans,” said Joanna Nathan, senior Afghanistan analyst at the International Crisis Group, a Brussels-based research institute. “But it is also being used to agitate and motivate the crowds by those against the government and foreign forces” in Afghanistan.

On Tuesday, protesters armed with assault rifles and grenades attacked the NATO base in the northern city of Maymana, which is manned by peacekeepers from Norway, Finland, Latvia and Sweden, local officials said.

Sayed Aslam Ziaratia, the provincial deputy police chief, said three protesters were shot and killed by Afghan and Norwegian forces and that 22 others were wounded. However, NATO said it only fired live ammunition into the air and rubber bullets. Five Norwegian peacekeepers suffered minor injuries.

Provincial governor Mohammed Latif said he suspected al-Qaida may have had a hand in the unrest. He said two men from eastern Afghanistan were arrested during the protest and were being interrogated.

“The violence today looked like a massive uprising. It was very unusual,” Latif said.

On Monday, about 2,000 protesters tried to storm the main U.S. military base at Bagram, the hub of the operations for some 20,000 American forces in the country. Police shot dead two protesters. A top local official said al-Qaida and Taliban militants incited the crowd.

Defense Minister Abdul Rahim Wardak told The Associated Press by telephone Tuesday that it was possible militants egged on the demonstrators, but he stressed the government has no evidence.

“Once these crowds get together, they often get out of control, here and in other countries,” he said. “But if this goes on, we’re going to have to take a closer look to see if there is more behind it.”

The unrest in Maymana prompted NATO to send 150 British troops to help secure the base, and two American A-10 attack aircraft were flown to the city. The U.N. evacuated nonessential staff.

In Washington, President Bush called Danish Prime Minister Anders Fogh Rasmussen to express “our solidarity and support.” A Danish newspaper first printed the cartoons of Muhammad in September, and they were reprinted this month by other European papers, setting off a new round of proptests.

Bush and Fogh Rasmussen agreed that all sides must move forward “through dialogue and tolerance, not violence,” White House spokesman Scott McClellan said.

In Copenhagen, Fogh Rasmussen showed no sign of diverting from his government’s stance that it cannot apologize for the actions of an independent newspaper, as demanded by governments in several Muslim nations.

Fogh Rasmussen called the protests “a growing global crisis.”

Iran’s supreme leader, Ayatollah Ali Khamenei, said Tuesday that publication of the caricatures was an Israeli conspiracy motivated by anger over the victory of the militant Hamas group in last mont’s Palestinian elections.

“The West condemns any denial of the Jewish Holocaust, but it permits the insult of Islamic sanctities,” Khamenei said.

Tuesday saw the biggest protest yet in Pakistan, where 5,000 people chanted, “Hang the man who insulted the prophet,” and burned effigies of one cartoonist and Denmark’s prime minister. The rally ended peacefully.

Thousands of Egyptians and Jordanians also demonstrated peacefully, calling for a boycott of Danish products and the cutting of ties with Copenhagen.