The exercises, larger this year than in the past, follow televised images from China on July 22 depicting a staged ground troop attack on a red tower and attached low-rises that resembled Taiwan's presidential compound.
China is Taiwan's only major potential military threat, though the two sides have shelved political differences since 2008.
They are separated by an ocean strait that is 160 km (100 miles) across at its narrowest point.
China's military, meanwhile, today announced three days of its own live-firing exercises in the Taiwan Strait, part of a program of more realistic training scenarios involving integrated units from the navy, air force and ground troops.
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It was not clear if the exercises starting yesterday were related to Taiwan's drills and China's Defense Ministry did not immediately respond to faxed questions seeking comment.
From a hillside in northern Taiwan about 1 kilometer (half a mile) into the ocean strait facing China, Taiwanese army troops fired howitzer shells, leaving a haze of smoke on land.
President Ma Ying-jeou wore a helmet and flak jacket to the staging area.
The Taiwanese drills, running Monday through Friday and known as the Han Kuang Exercise, involve 69 more aircraft than last year, Taiwan's government-funded Central News Agency reported. Many of the 63 drills will emphasize land-sea-air coordination.
Taiwan has shifted to designing its own hardware since 2010 as China mounted pressure on the United States, the island's chief overseas supplier, to stop arms sales. Taiwan's proposed 2016 budget includes USD 92.5 million for developing diesel-electric submarines over four years, as well.