BAGHDAD (Reuters) - Fresh explosions have rocked the Iraqi capital Baghdad as a succession of raids send black smoke billowing over parts of the city shaken by a fierce overnight blitz.

At dusk, a wave of new attacks shook the city outskirts with what witnesses described as a continuous explosions. New fires lit up the south and east, and tracer fire sliced through the night sky.

"They are definitely raising the intensity now," Reuters correspondent Khaled Yacoub Oweis said.

Iraqi ministers said three people had been killed and 207 wounded in the overnight attack, which was much heavier than on the first night of the U.S.-led war to oust Iraqi President Saddam Hussein.

The city's air raid sirens gave little or no warning of the daylight attacks on Saturday. There was little sign of Iraqi anti-aircraft fire, which had been intense during the overnight U.S. air and missile strikes on the centre of the city.

Iraqi Health Minister Umeed Midhat Mubarak said three people had been killed in the city overnight.

"Three people were martyred in Baghdad last night and we are preparing for more deaths because the situation is developing rapidly," he told a news conference.

Information Minister Mohammed Saeed al-Sahaf earlier told reporters that 207 civilians had been wounded overnight, making a total of 250 since raids started on Thursday.

Iraqi forces moved on Saturday to set oil-filled trenches ablaze around the city in an apparent bid to create a smokescreen to hinder air strikes by U.S. and British forces.

At least two dozen fires were raging around Baghdad, sending walls of thick black smoke into the sky. But the strategy might not prove effective attacks because many modern weapons use satellites to navigate.

FIREBALLS AND MUSHROOM CLOUDS

The overnight raids sent huge fireballs and mushroom clouds of smoke and debris into the night sky. They targeted Saddam's main palace on the banks of the River Tigris, government and military targets and other symbols of his rule.

Dazed parents said their children trembled with fear at the onslaught on the sprawling, palm-dotted city, which is home to over five million people.

Reuters correspondent Samia Nakhoul reported two explosions in central Baghdad as dawn was breaking. Less than an hour later, a third blast echoed from the city's outskirts. Air raid sirens wailed and ambulances raced through the streets.

In the first afternoon attack, a series of explosions started on the outskirts accompanied by the overhead rumble of warplanes, and gradually moved towards the centre of the city.

Air raid sirens sounded after the attacks, rather than before, and no anti-aircraft fire could be heard in the city centre.

At dusk, more large blasts were heard pounding on Baghdad's outskirts and new fires lit the darkening skies over the south and east of the city.

On the ground, small groups of soldiers with rifles were out on the largely deserted streets.

Shrapnel and glass littered the riverside Abu Nuwas Street, across the Tigris from Saddam's presidential compound.

In the compound, which houses the headquarters of Qusay, the younger son charged by Saddam with defending Baghdad, a building still smouldered. A small villa belonging to Vice President Taha Yassin Ramadan was destroyed.

Two other buildings, the Palace of Peace and the Palace of Flowers, were struck and fire engines were seen at the gates of the Jumhouriya (Republic) Presidential Palace, next to broken water pipes and other debris.

An air force centre in Saadoun Street in central Baghdad was also hit by repeated cruise missile strikes, while front of a ministry building close to the Rasheed Hotel was shattered.

Shaken residents said despite the terrifying fury of the attacks they would not take to the air raid shelters scattered around the city. Memories of an attack which killed hundreds of people in a shelter in the 1991 Gulf War still linger.

"We'd prefer to die at home than suffocate underground in a shelter," said Suad Saleh. "I won't go to the shelters".