IRAQI journalists yesterday walked out of a Baghdad news conference given by Colin Powell, US secretary of state, in protest at a lack of security and the killing of two Iraqi journalists by US troops.

''We declare our boycott of the conference because of the martyrs,'' said Najim al Rubaie, of Iraq's Distor newspaper, in a statement at the start of the news conference as Mr Powell and Paul Bremer, Iraq's US governor, looked on.

''We declare our condemnation of the incident which led to the killing of the two journalists...who were killed at the hands of the American forces.''

More than 30 Iraqi journalists then stood up and walked out.

Employees of the Dubai-based satellite television channel Al Arabiya said US soldiers opened fire on a car carrying an Arabiya crew on Thursday evening after another car ran through a checkpoint.

The protest coincided with South Korea becoming the latest US ally in Iraq to balk at sending troops to an increasingly violent peacekeeping effort, scrubbing plans yesterday for a mission to the Iraqi hotspot of Kirkuk.

South Korea promised to eventually dispatch the 3600 troops earmarked for Iraq, but only after it finds a safer location. The government, already worried about terrorism at home, cited security concerns in Kirkuk and US pressure to participate in ''offensive operations''.

The mission would make South Korea the largest coalition partner behind the United States and Britain. Deployment will now be delayed, possibly until June.

Kirkuk has seen rising ethnic tensions as Kurds, Arabs and Turkomen compete for control of the city, located in one of the world's richest oil-producing regions.

Spain's new government has already threatened to pull its 1300 troops by July after last week's terrorist bombings in Madrid.

And Aleksander Kwasniewski, the Polish president said his country was ''misled'' about whether Saddam Hussein's regime had weapons of mass destruction and also was considering an early troop pullout.

Staunch allies Australia and the Philippines, however, rushed to buttress the coalition amid signs of stress.

''Iraq is now on the cusp of a positive new chapter,'' Alexander Downer, the Australian foreign minister, said. ''Now is not the time for the international community to succumb to terrorist threats.''