Four passengers were killed and 33 others injured when a Tokyo subway train derailed and sideswiped a packed commuter train running in the opposite direction during rush hour Wednesday morning, police said.

The collision occurred just after 9 a.m. about 100 meters northeast of Nakameguro Station, in Tokyo's Meguro Ward, on the Hibiya Line operated by the Teito Rapid Transit Authority subway company, police said.

This is the first major accident Teito has seen in nearly 70 years of operation and the first time passengers' lives were lost.