MOSCOW -- Smugglers in Ukraine shipped 18 cruise missiles, each capable of carrying a nuclear warhead, to Iran and China at the beginning of the decade, Ukrainian prosecutors said yesterday.

The apparent sale to Iran of 12 of the Soviet-era Kh55 cruise missiles, which have a range of 1,860 miles, probably will add to concerns in Washington, D.C., over alleged efforts to develop nuclear weapons in Iran.

Allegations of the sales first surfaced last month in comments by a Ukrainian legislator, but public confirmation by the new administration of President Viktor Yushchenko came only yesterday.

Each missile is capable of carrying a nuclear warhead with a 200-kiloton yield at altitudes too low to be detected by radar, and their shipment has been portrayed as a significant leak of Soviet-era weapons technology.

Yuri Boychenko, an aide to Ukraine's prosecutor-general, said in a phone interview from Kiev, the capital, that sales had not involved the government of then-President Leonid D. Kuchma.

"It was a totally illegal deal, carried out by an international criminal group," Boychenko said.

But Hrihory Omelchenko, the legislator who went public last month with allegations of the smuggling operation, yesterday charged, "It is ridiculous [for prosecutors] to say that they have no information about the involvement of high state officials.

"The deal, or actually two deals, were from the very beginning monitored by Ukrspetsexport, the state-owned arms sale monopoly," Omelchenko said in a phone interview. "Kuchma was in the picture from the very beginning, and in other words he sanctioned the deals."

Omelchenko said the missiles were shipped to China in 2000 and to Iran in 2001. If the missiles were made operational, they could strike Israel if launched from Iran and Japan if fired from China or its neighbor, North Korea.

The Japanese government reportedly is worried that the six missiles allegedly shipped to China could have ended up in North Korea, which claims to possess nuclear weapons. China is a longtime nuclear power that possesses a variety of long-range missile types.

In Washington, State Department spokesman Adam Ereli said U.S. and Ukrainian authorities have discussed the alleged missile sales. "Ukraine has launched an internal investigation into the incident. That's certainly something we welcome," he said.

Ukrainian Foreign Minister Borys Tarasyuk, speaking to reporters during a visit to Belarus, said the country's new reformist government bears "no responsibility for what our predecessors have done" and "can only denounce past unauthorized transfers of arms.