BEIJING, OCT. 23 -- China said today the United States was "not reasonable" in imposing sanctions on high-technology sales in response to the alleged continued sale of Chinese-made Silkworm missiles to Iran.

{In the southern Persian Gulf, meanwhile, an Iranian speedboat attacked and set afire a Panamanian-flagged tanker early Saturday, gulf-based shipping sources said. There were no immediate reports of casualties.}

Yesterday, the State Department said the U.S. government was freezing a review on controls of high-technology items China can buy because of "rising tensions" in the Persian Gulf. The United States has pressed China for more than a year to stop supplying arms, including the surface-to-surface Silkworm missile, to the Tehran government.

In dismissing the Chinese complaints, Reagan administration sources in Washington said late today that Iran had sent some military personnel to China for training on jet fighter planes. One source, speaking on condition of anonymity, said a small group of Iranians "are in China and believed to be training on fighter planes."

The decision to censure China came after a Silkworm missile attack yesterday on a Kuwaiti oil terminal in the Persian Gulf, the third time in a week that Iranian Silkworms have hit targets in Kuwaiti waters. Iranian Silkworms last week hit two oil tankers, one owned by a U.S. company and the other flying an American flag.

China claims strict neutrality in the Persian Gulf conflict and insists it sells arms to neither side. It has acknowledged, however, that Chinese weapons may reach Iran through international arms markets.

United Press International reported the following from Beijing:

Iran's ambassador to China, Alaeddin Broujerdi, denied his country purchased the Silkworm missiles used in the attacks from Beijing. He said the missiles were captured from Iraq and copied by Iranian weapons manufacturers. Iraq has denied losing any Silkworms to Iran.

Speaking at a news conference , Broujerdi said Tehran has many more U.S.-made Stinger antiaircraft missiles than were earlier reported. He declined to say where it obtained the Stinger and Silkworm missiles.