Iraqi troops halted an advance by US forces up the Euphrates river, engaging them in battle near the Shi'ite holy city of Najaf, just 100 miles south of Baghdad, US and Iraqi officials said.
Journalists reported a limited clash with Iraqi troops southeast of Najaf that held up the US advance overnight. There is reported heavier fighting further up the river, close to Najaf itself.
Iraq's ruling party said in a broadcast statement that US forces had fled after a desert clash near the city, on the west bank of the Euphrates. The local leader of President Saddam Hussein's Baath party was killed in the fighting, it added.
US officers said they were confident of moving on quickly toward Najaf where they believed they could meet a division of Saddam's better-equipped Republican Guard.
The fighting near Najaf, a city of 420,000 and an important religious centre for Iraq's Shi'ite majority, would be the closest major ground warfare had come to Baghdad since Thursday.
The US military says it has secured a bridge across the Euphrates at the city of Nassiriya, 235 miles southeast of Baghdad. Iraq's information minister said on Sunday that its forces were still putting up resistance around Nassiriya.