"There is only one China in the world and Taiwan is an inseparable part of its territory," the embassy said in its statement Saturday, reiterating the internationally-accepted "One China" policy.
China considers the self-ruled island as a breakaway province that should be reunited with the mainland under the “One China” policy. Nearly all countries of the world, including the United States, recognize that sovereignty.
Under that policy, countries are not allowed to have formal relations with Taiwan.
The embassy also described the visit by the 90-member Czech delegation as "a serious interference in China's internal affairs."
The embassy called on the Czech government to "take specific steps to remove the unfavorable impact of the said incident."
Chinese Foreign Minister Wang Yi has also described the visit as a "provocation." He said China would make Czech Senate Speaker Milos Vystrcil, who led the delegation, "pay a high price for his short-sighted behavior."
The Czech Foreign Ministry then summoned China's ambassador to Prague. Beijing followed suit, further escalating tensions.
The center-left government in Prague, led by Czech President Miloš Zeman and Prime Minister Andrej Babis, favors closer ties to China. But Vystrcil is a member of the right-wing opposition Civic Democrats and is not bound by the One China policy.