Police in Italy have arrested two American students.
They the pupils are connected to the killing of a policeman in central Rome.
According to a statement from Italian military police Carabinieri, the students are also being held for attempted extortion.
The students allegedly stabbed 35-year-old Mario Cerciello Rega to death on Friday.
Another police officer was injured in the incident.

Israeli strike kills one in Gaza as sides trade blame for truce violations
UK police say mass stabbing on train not terrorist incident, two arrested
Israel urges Lebanon to disarm Hezbollah under ceasefire terms
Russian attacks on Ukraine kill two
Kenya landslide death toll rises to 22
Fire at store in northwestern Mexico leaves at least 23 dead
Ukrainian drone strike hits key Russian oil port
Tanzania's Hassan declared landslide winner in election marred by violence
