Several city police officials were scheduled to be in Moscow this weekend to learn about the bomb that ripped through a subway car there during rush hour Friday morning, killing 39 people and wounding more than 120.

The trip will serve as another learning tool for the New York Police Department's counterterrorism efforts. NYPD officials asked permission to send police to Moscow.

Friday's bombing was the deadliest terrorist blast in the capital since Russia launched its second war in Chechnya.

President Vladimir Putin blamed the explosion on Chechen rebels and said it was aimed at sowing chaos before next month's presidential election.