The execution was condemned by the European Union, which had raised Wo's case during a meeting in Beijing on Friday on human rights, and by the United States, which had sought a stay on grounds of lack of due process.
"This execution seriously undermines the spirit of trust and mutual respect required for this EU-China dialogue on human rights," said a statement from the presidency of the EU, which is held by France.
The strong words from the EU came at the end of a week in which Beijing cancelled an upcoming EU-China summit in protest against French President Nicolas Sarkozy's plans to meet with the Dalai Lama next month.
Wo's execution by gunshot on Friday morning was confirmed through the Austrian embassy in Beijing, said his daughter Ran Chen, who arrived in the city this week for a last visit. Wo's daughters are Austrian citizens.
"His life was taken from him before he or our family could say our last goodbyes. The entire process–from arrest to execution–was conducted in a way that was degrading to both my father and our family," Chen and her sister Di said.
"We were all misled, led to have false hope, denied the fundamental right to be informed, and forced to suffer."
Wo's death sentence for passing sensitive information to Taiwan, a self-ruled island which China considers as a breakaway province, had been upheld in February this year by the Beijing High Court but had been delayed pending a review. Chinese citizen, Guo Wanjun, was accused and condemned in the same case.
Far Short of International Standards of Due Process
Wo, who ran a medical research company, suffered a stroke in a detention centre in 2005. He was forced to confess without access to a lawyer, but later recanted that confession and said he was innocent, Amnesty International said, citing his family.
He was found guilty of discussing the health of senior Chinese leaders, and of sending along information from a magazine, Amnesty said."We are deeply disturbed that Wo Weihan was executed this morning. According to available information, Mr Wo's arrest and trial on charges of espionage and endangering state security, fell far short of international standards for due process," a U.S. embassy spokesman said on Friday, adding that the U.S. ambassador and other officials had raised the case repeatedly.
Wo's daughter Ran Chen was summoned to Beijing this week, for what she was told would be the last meeting with the father she had not seen in four years.
But Chen and her stepmother did not have the heart to deliver their carefully prepared farewells, when they saw that Wo himself had not been informed that they were coming, and did not have any information about his fate.
"Because he did not know about a looming execution, he was hopeful and did not leave any final words or will with our family," Chen said.
They were not allowed to give Wo letters from his brothers or discuss his case, although they could bring in photographs to show their father, who was handcuffed on the other side of a glass partition, Chen told reporters on Thursday.
China keeps secret the number of prisoners it executes, but the Dui Hua Foundation, which conducts dialogue with China on human rights, estimated the number of executions at between 5,000 and 6,000 a year in 2007.