China says military exercises by its navy, air force and other departments are underway in six zones surrounding Taiwan.

The drills were prompted by a visit to the island by Speaker of the U.S. House of Representatives Nancy Pelosi this week and are intended to advertise China’s threat to attack the self-governing island republic in response to moves to solidify its de facto independence from Chinese rule with support from key ally the U.S, the Associated Press reported.

China’s official Xinhua News Agency said the exercises were joint operations focused on “blockade, sea target assault, strike on ground targets, and airspace control.” 

Taiwan has put its military on alert and staged civil defense drills, while the U.S. has numerous naval assets in the area.

The drills are due to run from Thursday to Sunday and include missile strikes on targets in the seas north and south of the island in an echo of the last major Chinese military drills aimed at intimidating Taiwan’s leaders and voters held in 1995 and 1996.

The exercises involved troops from the Navy, Air Force, Rocket Force, Strategic Support Force and Logistic Support Force under the Eastern Theater Command, AP reported.