Two Palestinian boys believed to be about 12 or 13 years old stabbed an Israeli guard in east Jerusalem Tuesday before the guard shot and wounded the younger boy, police said.

Investigators say the attack unfolded on a train. They say the boys, who were related, moderately wounded the guard. Other passengers subdued the older boy, police said.

The wounded child was being treated at a hospital.

An amateur video that surfaced on a Palestinian website showed plainclothes Israeli security forces wrestling a young boy, presumably one of the attackers, to the ground and taking off his clothes and shoes. The boy was stripped to his underwear as the security men shouted at him.

Later Tuesday, Israeli forces killed a 37-year-old Palestinian man outside the Old City as he allegedly chased guards while wielding a knife, police said. Israeli police said forces foiled an additional attack in Abu Dis, an Arab neighborhood in east Jerusalem. Police spokeswoman Luba Samri said a Palestinian tried to stab forces at a checkpoint before he was shot dead.

Jerusalem had been relatively calm over the last two weeks as the focus of a two-month wave of Palestinian attacks, mainly stabbings, shifted to the West Bank, where Israeli troops have also regularly clashed with Palestinian protesters.

Most of the Palestinian attackers have been in their late teens or early 20s.

The trial meanwhile opened for 13-year-old Ahmed Manasra, who along with his 15-year-old cousin Hassan stabbed two Israelis in east Jerusalem in mid-October, according to the indictment. Police shot and killed Hassan and a passing car ran over Ahmed. The Israelis, aged 20 and 13, survived their wounds.

Palestinian President Mahmoud Abbas caused an uproar in Israel when he erroneously claimed in a televised speech that Israelis had "summarily executed" Ahmed, who at the time was recovering at an Israeli hospital.

Israel promptly accused Abbas -- as it has done repeatedly in the past months -- of fomenting violence with what it says are incendiary comments.

Palestinians were enraged by video that surfaced on social media showing Ahmed lying in the street, his head bloodied, as bystanders curse him and shout "Die!" in Hebrew. The video made no mention of the preceding attack.

Israelis were shocked by a separate security camera video that appearing to show the two young cousins wielding knives and chasing a man, and later stabbing an Israeli boy as he got on his bicycle outside a shop after buying some candy.

Rights groups have alleged that Israeli troops have used excessive force against Palestinians, in some cases shooting and killing suspected attackers who the groups say could have been arrested.

On Monday, Palestinian media released footage showing Jerusalem police questioning Manasra.

In the video, police officers showed him the security camera footage of the attack. One of the officers shouts at him, "Is this you, this person?" as the teen cries and says he doesn't remember.

It was unclear how Palestinian media obtained the video or who filmed the Israeli investigation.

Attorney Lea Tsemel, who is representing Manasra, said she may contest the investigation based on the video. "You cannot terrify or threaten or tempt for the purpose of achieving a confession," she said.

Samri, the police spokeswoman, said the investigation was conducted "with professionalism and without bias."

Since mid-September, 12 Israelis have been killed in Palestinian attacks, mostly stabbings. Seventy-seven Palestinians have been killed by Israeli fire, including 50 said by Israel to have been involved in attacks or attempted attacks. The other Palestinians died in clashes between stone-throwers and security forces.

The latest bloodshed was triggered by unrest at a major Jerusalem shrine revered by both Muslims and Jews, and quickly spread across Israel, the West Bank and the Gaza border. Israel accuses Palestinian political and religious leaders of inciting the violence. Palestinians say the unrest is the inevitable result of nearly 50 years of Israeli occupation and no hope for gaining independence.

The Associated Press contributed to this report.