Prime Minister Mohammad Ali Rajai warned Britain yesterday that Iran would react appropriately unless it stopped carrying out "cruelties" against Iranian students arrested in London, the state radio reported.

He was echoed by the speaker of the Iranian parliament, Ali Akbar Hashemi Rafsanyani, who labeled Britain a U.S. "satellite." He read the legislators a letter from the detained Iranians and said Britain had become an extension of the United States.

Rajai's warning came in a reply, addressed to the British Embassy in Tehran, to a message of congratulation from the British government on Rajai's appointment last month as premier. An embassy spokesman said the reply had not yet been received.

In his message Rajai said, "The Iranian people want a review of the attitude of the British government toward the Islamic revolution of Iran, as well as an urgent end to biased propoganda against the Islamic republic."

Forty-five Iranian students arrested during a demonstration outside the U.S. Embassy in London are still detained there awaiting a decision by the British home secretary on recommendations by courts that they should be deported.

The state radio also reported that nine persons were executed, including six convicted of arson in an August 1978 fire that claimed 430 lives in a movie theater in Abadan.

Meanwhile, President Abol Hassan Bani-Sadr was quoted by the official Pars News Agency as saying he had the choice.

"If I were free to choose, I wouldn't stay in this office a moment longer, Bani Sadr reportedly said. "But I feel a duty to stay on and I fear neither accusations nor insults."