China regards Taiwan as part of its territory and for years has been ramping up military, diplomatic and political pressure on the island to accept its claims of sovereignty.

Taiwan says cyberattacks have also increased as Beijing uses a range of "greyzone" methods to harass the island -- tactics that fall short of an act of war.

Most of the daily attacks received by Taiwan's Government Service Network were attributed to China's "cyber force", the National Security Bureau said in a report on Sunday.

Defence, telecommunications and transport were among the top targets, with many of the cyberattacks "effectively detected and blocked", it said.

"The growing numbers of attacks pinpoint the increasingly severe nature of China's hacking activities," the report said.

"Its techniques have become increasingly sophisticated and covered a wide range of targets, such as government agencies, critical infrastructure and high-tech manufacturing industry."

Chinese hackers carried out Distributed Denial of Service attacks on Taiwan's transport and financial sectors when Beijing held military drills near the island, "intending to intensify the harassment effect and military intimidation", the bureau said.

Several countries, notably the United States, have voiced alarm in recent years at what they say is hacking activity backed by Beijing targeting their governments, militaries and businesses.

China has denied the allegations, previously insisting it opposes and cracks down on all forms of cyberattacks.

Beijing last week rejected accusations that a China state-sponsored actor was behind a cyber breach at the US Treasury Department, calling the claims "groundless".