Security agents have arrested 17 people allegedly trained in Pakistan who they believe planned to launch homicide attacks in three Afghan provinces, Afghanistan's intelligence agency said on Wednesday.

The U.N. refugee agency, meanwhile, said tens of thousands of people have been driven from their homes by recent fighting in southern Afghanistan, and the number could increase.

The 17 people were detained in Nangarhar, Kunduz and Kabul provinces and told authorities they attended training camps in Pakistan, according to Said Ansari, spokesman for Afghanistan's intelligence agency. It was unclear when they were detained.

CountryWatch: Afghanistan

Ansari said militants in Pakistan encourage fighters to carry out homicide attacks by telling them that girls in Afghanistan are wearing un-Islamic clothes or studying subjects in school unrelated to Islam.

The would-be bombers trained in Shamshatoo, an Afghan refugee camp near Peshawar, and at another camp near Data Khel in Pakistan's semiautonomous North Waziristan tribal region, Ansari said.

"They are telling those people that they should conduct suicide attacks because the foreigners who are here are doing bad things in Afghanistan that are unacceptable in an Islamic country," Ansari told a news conference.

Few details were provided on the 17. One was an Afghan, said Ansari, who did not reveal the nationalities of the others.

Pakistan's government signed a deal with pro-Taliban militants on Sept. 5 to end fighting that broke out in North Waziristan after the U.S.-led invasion of Afghanistan in October 2001. Under the deal, militants agreed to not carry out violent acts, fan extremism or send fighters into Afghanistan to attack local forces of foreign troops.

Pakistan's top military spokesman said Pakistan had no information on the 17 arrests and urged Afghan officials to convey its information to Pakistani authorities.

"If there is any such evidence, this should be shared with us officially through the fastest channels so that we can verify it and take appropriate action," Maj. Gen. Shaukat Sultan told The Associated Press. "Sharing of such information with the media is absolutely unwise and illogical."

Taliban-linked militants have stepped up attacks this year, including the use of suicide and roadside bombs. It's been the deadliest period in Afghanistan since late 2001, when U.S.-led forces ousted the Taliban regime for hosting Usama bin Laden.

Ansari said 160 civilians have been killed and 500 wounded in 90 suicide attacks over the last two years and that most suicide attackers were Afghan, Pakistani or Chechen. He said there have been 72 suicide attacks since March 21.

Some 184 schools have also been burned down or destroyed this year, Ansari said, compared with about 145 that were attacked last year, according to the Education Ministry.

Afghan officials say Pakistan turns a blind eye toward militant activity in its tribal areas, and that those fighters regularly stream across the border into Afghanistan.

Afghan President Hamid Karzai also called on Pakistan recently to crack down on religious schools — known as madrassas — which he claimed fanned a culture of hate and extremism.

U.S. officials say attacks on their country's troops near Afghanistan's eastern border have increased threefold since the North Waziristan agreement that was supposed to prevent such activity.

Ansari said Pakistani forces "are not preventing the cross-border activities of our enemies."

Pakistani authorities deny charges of not doing enough to stem the flow of militants and weapons from its territory into Afghanistan. But they acknowledge that the porous nature of the border makes it virtually impossible to completely seal.

The fighting since July has uprooted between 80,000 and 90,000 people in the southern provinces of Kandahar, Uruzgan and Helmand, said Jennifer Pagonis of the U.N. High Commissioner of Refugees.

"This fresh displacement adds new hardship to a population already hosting 116,400 people earlier uprooted by conflict and drought," she said Tuesday in a statement.

"We expect further displacement may take place until conditions are safe for the population to return to their homes," she added.

U.N. aid agencies have distributed plastic sheets, blankets, warm clothes for children and other relief items to more than 3,000 families in Panjwai and Zhari districts of Kandahar province, Pagonis said.

The resurgence of the Taliban has triggered an escalation of violence in southern Afghanistan in the past few months, and NATO troops that took command of the southern provinces two months ago have been struggling to stem the violence.

In Helmand, clashes Sunday left 10 people dead, including five civilians. The civilians were killed when their vehicle hit a land mine on a road usually used by NATO and Afghan security forces.