Taiwan said on Tuesday that China was conducting its largest maritime operations in nearly three decades, sending nearly 90 naval and coast guard vessels into waters stretching from the southern Japanese islands to the South China Sea.

Taiwanese defense officials said the scope of the deployment suggested that China was not only trying to show that it could choke the self-governed island, but also that it could block American allies in the region like Japan and the Philippines from coming to Taiwan’s defense.

China has “extended their military strength outward,” Gen. Hsieh Jih-sheng, a senior official in Taiwan’s ministry of defense told reporters. “The numbers are indeed astonishing,” he said, referring to the surge of Chinese vessels in the waters. Sun Li-fang, a spokesman for Taiwan’s defense ministry, said the maritime operations were the largest that Taiwan has seen since 1996.

The officials said that Taiwan was on high alert in response to the Chinese ships, many of which were in waters off Taiwan’s southwest, east and northwest coasts.

China’s intentions were not immediately clear. There were no official announcements from Beijing that its forces were holding exercises. A foreign ministry spokeswoman, asked on Tuesday if China was conducting drills near Taiwan, deflected the question.

General Hsieh suggested that China’s silence about the large deployment was aimed at catching the island off guard.