China began a series of unprecedented, large-scale military exercises Thursday that could effectively choke off Taiwan just hours after U.S. House Speaker Nancy Pelosi visited the self-ruled island, infuriating Beijing and triggering fears of a new crisis across the Taiwan Strait.

The almost five days of drills are set to be the largest ever around Taiwan, which Beijing claims is part of its inherent territory, and will involve People’s Liberation Army (PLA) air, naval, land and amphibious forces, as well long-range live-fire shooting and conventional missile test launches, according to the Chinese authorities.

PLA warships were seen gathering around Taiwanese waters around noon to mark the official start of the drills, with Taipei reporting multiple firings of Chinese Dongfeng ballistic missiles into waters off northeast and southwest Taiwan shortly after.