All diesel-engine buses owned by major bus operators in Tokyo will be equipped with devices to cut diesel emissions by the end of June, Tokyo Gov. Shintaro Ishihara announced Wednesday.

The Tokyo Bus Association, whose 91 members operate 8,400 buses, will introduce devices to cut particulate matter emissions to 3,600 of the 4,600 diesel-engine buses in their fleets by the end of June, Ishihara told a regular news conference held in the metropolitan government building. The remaining 1,000 will either be scrapped or replaced with newer vehicles.

"I highly appreciate the decision of the bus operators," Ishihara said. "However, the central government should have taken this kind of initiative to protect the environment on a national level."

The Tokyo Metropolitan Government, along with the prefectural governments of Saitama, Chiba and Kanagawa, plan to introduce more stringent regulations regarding diesel-engine vehicles in October and had been calling for the bus operators to equip their buses accordingly.