According to the Pentagon, the incident happened at about 11am Iraqi time when two American F-16s intercepted two Iraqi MiGs about 20 miles inside the protected zone south of the 32nd parallel. The Iraqi planes ignored a verbal warning and 'turned to confront' the F-16s. One was shot down, according to the CNN network, by an air-to-air missile.
President George Bush, beginning a two-day holiday in Texas, said the Iraqi President, Saddam Hussein, had made 'a big mistake'. Mr Bush added: 'We are not threatening anybody. But we must enforce those resolutions. I've heard that it might be some test of our will near the end of my presidency, but those F-16s sent the message to him pretty clearly.'
In an interview on US television, the CIA director, Robert Gates, suggested the Iraqi breach of the no-fly rule imposed by the allies last August to protect Shia Muslims living in southern Iraq was further proof of Baghdad's impatience and frustration with the restrictions imposed after its defeat in the 1991 Gulf war.
'It seems to me part of a pattern over the last few months of increasing Iraqi aggressiveness,' Mr Gates said on the CBS programme Face The Nation. But, he added, it was not clear on this occasion whether the aircraft had strayed off course or were challenging the ban.
In fact, Iraq's southern front has been relatively quiet since the US, Britain and France began to enforce the sanctuary zone for the Shias on 26 August. Yesterday's was the first Iraqi intruder to be shot down in the south since then; over the period the allies have flown more than 7,500 sorties without incident, at a rate of 40 to 120 a day.
Most of the recent tension has been in the north of the country, where allied and UN observers have been increasingly alarmed at an apparent Iraqi army build-up on the borders of the protected zone north of the 36th parallel, set up shortly after the Gulf war to safeguard Iraq's Kurdish population.
A few hours after the clash, a statement read on Iraqi television protested at the destruction of the aircraft which was 'on a routine patrol over our national territory and within our national borders'.
The statement assailed 'this criminal act perpetrated by the poles of imperialist and Zionist aggression'. Iraq reserved the right to respond 'in a suitable manner at an appropriate time'. The military spokesman did not say what action Iraq might contemplate.
The Pentagon said that not one but two incidents took place yesterday. In the first, about 40 minutes earlier, two other Iraqi jets had entered the southern no-fly zone, but flew off before two American F- 15s could identify and challenge them.
After the MiG was shot down in the second confrontation, an Iraqi helicopter was allowed to visit the crash site and then return to its base. The fate of the Iraqi pilot was not known. The measures to protect the Shia population were imposed under UN Security Council resolution 688, after Saddam Hussein had used Iraq's air might to crush the rebellion which erupted in the south against his Sunni-dominated government immediately after the Gulf war.
It had been widely expected in Washington that President Saddam would stage some provocation in the Iraqi theatre to test the resolve of President-elect Bill Clinton, but not until closer to Mr Clinton's inauguration on 20 January.
Mr Clinton yesterday warned Iraq against mistaken tests of international solidarity. 'This is part of a series of tests of international resolve to bring Iraq into compliance with United Nations resolutions,' Mr Clinton said. 'Saddam Hussein is mistaken if he believes the US or the UN lacks that resolve. I support efforts to bring Iraq into compliance.'Reuse content