[CNN] Kabul, Afghanistan (CNN)Afghan security forces started retaking parts of Kunduz from the Taliban, officials said, one day after the key city had largely fallen in a major victory for the insurgents."A big military operation to clear all Kunduz city is about to start," Interior Ministry spokesman Sediq Sediqqi said Tuesday.
U.S. forces joined in the military action, launching an airstrike in Kunduz on Tuesday, said Brian Tribus, spokesman for U.S. forces in Afghanistan.
The Kunduz prison, a police compound and the neighborhood of Zir Dawra are among the areas Afghan forces have secured, Sediqqi said.
A day earlier, Sediqqi said Kunduz had largely fallen into "the hand of enemies." Kunduz is the largest city to be overrun by the Taliban since 2001.
Sayed Sarwar Hussaini, a spokesman for the Kunduz police chief, said Taliban insurgents seized the main roundabout in the city and made it to the prison, where they freed more than 500 inmates.
The Taliban also claimed to have seized a 200-bed hospital -- posting photos to social media that they claimed proved their control of the facility.