BERLIN -- Germany's federal prosecutor is checking whether he should take over the investigation into a fatal stabbing in Hamburg earlier this month, his office said Sunday.

A spokesman for the prosecutor's office told the German news agency dpa that the prosecutor is looking into the case following a statement by the IS-run Aamaq news agency on Saturday saying "a soldier of the Islamic State" stabbed two people in Hamburg on Oct. 16.

"We are aware of the statement and have to check the content thoroughly in regard to its reliability," said the spokesman who was speaking on condition of anonymity in line with department policy.

Two teenagers, a 16-year-old boy and a 15-year-old girl, were sitting on the waterside of a Hamburg lake that day, when a man approached them from behind, stabbed the boy several times with a knife and then pushed the girl into the water. The attacker fled afterward. The boy was taken to a hospital where he subsequently died. The girl who was pushed into the water wasn't injured, but was taken to a hospital for psychiatric treatment after the attack.

Different from the IS claim, only one person was stabbed.

Hamburg police are still looking for the attacker, whom they have described as a male from 25 to 30 years old. The attack at Aussenalster lake, which is a popular leisure time destination, had shocked the citizens of Hamburg for its cold-bloodedness. The spot where the attack took place has been decorated by friends of the teenage couple with flowers, red memorial candles and balloons.

In its statement, the Aamaq news agency said, "the attack was carried out in response to target citizens of the coalition countries that fight the IS." It did not identify or give a name for an attacker.

Hamburg police spokesman Timo Zill said it was too early to speculate about the possible attacker and his motive, but added that a homicide squad was working around the clock to solve the case.

"We currently have a few leads that we are looking at," Zill told German news channel n-tv. He did not want to give further details because of the ongoing investigation.

In July, two attacks carried out in Germany by asylum seekers were claimed by IS. Five people were wounded in an axe rampage on a train near Wuerzburg and 15 in a bombing outside a bar in Ansbach. Both of the attackers were killed.

Earlier this month, a 16-year-old German-Moroccan girl went on trial for allegedly stabbing and wounding a police officer in Hannover at the behest of the Islamic State group.

A Syrian migrant who was suspected of planning to carry out a bomb attack killed himself in prison two days after being arrested this month in Leipzig.

Germany's top security officials have long warned that the country is in the crosshairs of terror attacks by Muslim extremists. So far, no IS attack has claimed any fatalities in Germany other than the deaths of the two attackers in July.

Maamoun Youssef contributed reporting from Cairo.