THE propaganda machinery has continued to give out signals that Prime Minister Mr Li Peng, who has not appeared in public since April 24, is attending to affairs of state. In a dispatch yesterday, the New China News Agency (NCNA) said Mr Li and President Mr Jiang Zemin, sent a congratulatory message last Saturday to Eritrean President Mr Issaias Afwerki on its independence. NCNA quoted Mr Jiang and Mr Li as saying in the message that ''China appreciated the Eritrean Government's devotion to national reconciliation and economic development at home while pursuing a policy of good-neighbourliness, friendship and non-alignment internationally''. However, the NCNA did not indicate the state of Mr Li's health. Nor did it explain why it waited for three days before publicising the message. Last night, the television station CCTV also reported that Mr Li had sent a message to a committee in charge of preparatory work for the Three Gorges project. Mr Li was quoted as calling upon the dam experts to live up to their ''responsibilities to the nation, science and history''. While Chinese sources said Mr Li had suffered at least one heart attack, officials including Executive Vice-Premier Mr Zhu Rongji have said the premier had caught a cold and that he was recuperating. Meanwhile, diplomatic circles in Hongkong and Beijing yesterday were speculating that Mr Li had in the past week had an operation in relation to his heart ailment, and that the operation was ''not totally satisfactory''. Mr Li's son, who was doing business in Hainan Island, is reported to have returned to the capital to be with his father. The 65-year-old premier is believed to be staying in Hospital 301 or 305, both military medical institutions.