BEIJING, June 21 (Reuters) - China on Friday issued guidelines on imposing criminal punishment on "diehard Taiwan independence" separatists for conducting or inciting secession, state news agency Xinhua reported.

China, which views democratically governed Taiwan as its own territory, has stepped up pressure on the island after the inauguration last month of Lai Ching-te as president, a man Beijing despises as a "separatist", including staging war games shortly after he took office.

The new guidelines say China's courts, prosecutors, public and state security bodies should "severely punish Taiwan independence diehards for splitting the country and inciting secession crimes in accordance with the law, and resolutely defend national sovereignty, unity and territorial integrity".

The guidelines are being issued in accordance with laws already on the books, including the 2005 anti-succession law, Xinhua said.

That law gives China the legal basis for military action against Taiwan if it secedes or seems about to.

China has taken legal measures against Taiwanese officials before, including imposing sanctions on Hsiao Bi-khim, Taiwan's former de facto ambassador to the United States and now the island's vice president.

Such punishments have little practical effect as Chinese courts do not have jurisdiction in Taiwan, whose government rejects Beijing's sovereignty claims.

Lai has repeatedly offered to hold talks with China but has been rebuffed. He says only Taiwan's people can decide their future. (Reporting by Beijing newsroom; Writing by Ben Blanchard; Editing by Christopher Cushing and Miral Fahmy)