KABUL, Afghanistan - Amid screams of "Suicide bomber! Suicide bomber!" an insurgent detonated his vest of explosives Saturday, killing at least four people at a sports field in northwest Afghanistan.

It was the latest in a spate of attacks that have hit nearly every corner of the country in recent weeks. A roadside bomb also killed nine people Saturday near the eastern city of Khost.

The suicide bomber struck a game of buzkashi, a traditional Afghan sport in which players on horseback wrangle for a headless goat carcass, said Abdul Haq Shafiq, governor of Faryab province.

"The people and the police became suspicious of the bomber," Shafiq said. "People started running. Everyone was scared. The people called out, 'Suicide bomber! Suicide bomber!' and then the bomber blew himself up."

Besides the dead, 19 people were wounded, said Shafiq. About 2,000 people were at the event when the blast occurred.

Three men, two women and four children also were killed when their vehicle hit a roadside bomb in the insurgent-ridden Lakan area of the capital of Khost province, according to the Afghan Interior Ministry.

Suicide attacks have picked up across the country since late January.

The Afghan intelligence service announced the arrests of a Pakistani boy and two teenagers -- one from Afghanistan and the other from Pakistan -- who claimed they had been coerced into becoming would-be suicide bombers.

All three appeared at a news conference and recounted stories of how militants forced them into becoming suicide attackers for the insurgency. The intelligence service wanted to highlight claims that have surfaced in the past two weeks of insurgents trying to persuade young people to give up their lives for the insurgency.

Akhtar Nawaz, 14, from South Waziristan in Pakistan, said six men in a vehicle nabbed him off the street while he was walking home from school.

"They told me that I had to carry out a suicide attack," Nawaz told reporters. "I told them I didn't want to, but they forced me to go with them. They told me that there were foreigners in Afghanistan and if I carried out a suicide attack, I would go to heaven."

Nawaz said the men took him to various locations and taught him how to shoot a pistol, ride a motorbike and detonate a suicide vest. His mission, he said, was to shoot guards at an Afghan military compound in Khost province, then to ride inside and detonate his cache of explosives. He said he was told that if the detonation button on his vest didn't work, he should detonate the explosives by shooting himself with the pistol.

He said he was driven to Khost and shown the target but decided not to go through with the attack at the last minute, turning himself in to Afghan security forces instead. He remains in custody.

Ghamia, a 19-year-old shopkeeper from the southern city of Kandahar said he was approached several times by militants trying to persuade him to become a suicide attacker to ensure himself a place in heaven. For his service, he said the militants promised to give his parents 500,000 Pakistan rupees ($5,800).

"They told me 'This is a good job. We are paying 500,000 rupees to your parents and you'll go to heaven. What more do you want?"' he said.

Over two months, he was taken to various locations, sometimes while blindfolded in the car. Intelligence service officials, acting on tips, arrested him in Spin Boldak district of Kandahar province along the Pakistani border before he ever received instructions for carrying out a suicide attack.

Yasur, 19, of Peshawar, Pakistan, was arrested while eating lunch at a hotel in Laghman province, east of Kabul.

Yasur said four men in Pakistan encouraged him to join the insurgency as a suicide bomber. He said he was eventually taken to the east side of Kabul where he stayed with a cleric named Zunelabidin.

In a videotape provided by the intelligence service, the cleric told authorities that he had helped the Taliban two or three times in the past year to get equipment, including wire for making bombs. Zunelabidin, who was arrested at the hotel with Yasur, said he also had provided a place for suicide bombing recruits to stay.

At least five high-profile suicide bombings have struck security forces and civilians across Afghanistan since January.

One bomber struck an upscale supermarket frequented by foreigners in Kabul on Jan. 28, killing eight people. Seventeen days later, another suicide bomber in Kabul attacked a Western-style shopping mall, killing two security guards.

Taliban insurgents wearing explosive vests attacked a police headquarters in Kandahar on Feb. 12, unleashing an arsenal of car bombs, automatic rifle fire and rocket-propelled grenades and killing at least 18 people, many of them police.

In Khost, a suicide attacker in a bomb-laden car struck a police station on Feb. 18, killing 11 people.

In northern Afghanistan, a suicide bomber blew himself up Monday at the entrance to an Afghan government office in Kunduz province, killing at least 30 people, including many who were waiting in line to obtain government identification cards, police said.