WASHINGTON (AFP) - Dozens of police officers swarmed one of Washington DC's busiest stations with dogs and bomb technicians during Tuesday's morning rush hour, to demonstrate that the US capital city's transit system can thwart possible terror attacks.

At around 7:30 am (1330 GMT), some 50 officers from various Metro police units -- including its new anti-terror team, special response teams and criminal investigators -- began their work at the Union Station subway stop near the US Capitol building that houses Congress.