Air Force One, carrying Clinton, his wife Hillary and a handful of senior US officials comprising a fraction of the president's entourage of about 1,000 arrived at Beijing international airport tonight to a waiting crowd of American and Chinese officials headed by Politburo Standing Committee member Hu Jintao.

Earlier on the day, Clinton had criticized the detentions of a number of mainland pro-democracy activists - including two men in the ancient silk road city of Xi'an, where Clinton arrived last evening for a grand welcoming ceremony on the first leg of his five-city China tour. Two of the men, dissident Yang Hai and human rights lawyer Zhang Jiankang, were released from this evening.

Zhang was detained just prior to being interviewed by America's ABC News and told by police he did nothave the proper authorization to talk to foreign journalists. He was released six hours later, said Frank Lu Siqing, spokesman of the Hong Kong-based Information Centre for Human Rights and Democratic Movement in China.

Confirmation of the releases came after US Ambassador to China James Sasser lodged a formal protest against the Chinese Government earlier today, saying Beijing had ``basically not adequately explained'' the detentions.

Sasser said China was generally headed in the right direction but the human rights situation was ``terrible'' and its improvement was a top priority for Clinton on this trip. Beijing's reaction was swift and cutting. China's foreign ministry lashed out at media reports of the detentions, saying the ``so-called arrests of dissidents by the Chinese side are a rumour created out of ulterior motives,'' a spokesman said by telephone in Beijing. The foreign ministry spokesman added that Beijing remained opposed to interference in China's internal affairs ``by any foreign countryunder the excuse of human rights.'' The police is yet to release a fourth dissident, Li Xiaolong of the southern city of Guilin, who was taken from his home on Wednesday, Lu said.

Clinton is scheduled to arrive in the picturesque city on July 2. Clinton is scheduled to spend his first night in Beijing at the leafy compound of the Diaoyutai State Guest House on the west side.