AMMAN, JORDAN, JAN. 17 (THURSDAY) -- Thousands of Baghdad residents had fled by the time U.S. warplanes began bombing the center of the city early today.

According to reports broadcast by television correspondents in Baghdad, U.S. warplanes appeared to have hit a communications tower, an oil refinery and runways at the airport. Air raid sirens were sounded through the city and antiaircraft rounds exploded. The sky lit up with anti-aircraft fire, correspondents in the Al Rasheed Hotel reported.

"There were loud explosions, obviously bombs, in three parts of the city," a Cable News Network correspondent said in a telephone report from the city. "It looks like the Fourth of July" in Washington. "You can hear the bombs now. They just got the main telecommunications center . . . the planes are circling, . . . apparently coming back for more targets," he added.

Baghdad had waited for war with anxiety earlier in the day, as many residents quietly abandoned the city for farflung towns in the countryside and others huddled with relatives for moral support, according to travelers arriving from the Iraqi capital and several Baghdad residents reached by phone.

Two Baghdad residents said some families had fled to the northern mountains, others to resort towns near the Iranian border and still others to the southern cities of Najaf and Karbala, which are Shiite religious centers.

Refugees had apparently fled to these cities in the expectation that American planes would not strike near holy sites out of fear of reprisals from Moslem fundamentalists.

"Baghdad is like a ghost town," said one traveler who reached the Jordanian capital before the bombing began. "The streets are deserted and the souks are calm. You don't know what is going on inside each home, but there are signs of increasing apprehension," he added.

Those who had opted to stay behind were trying to carry on with their lives, although offices closed earlier than usual, and shops and restaurants were shuttered, one resident said.

A middle-aged housewife said her elderly aunt had moved in with her family so she would not be alone, but insisted that they would not move out of their home. "We are fine and our spirits are high," she said defiantly before the bombs began to fall. "We appreciate your call, but there is nothing to worry about," she said.

"Our spirits are high most of the time, but our mood goes up and down," admitted a businesswoman, who said she could not leave her parents at a time like this. Halfway in the conversation, the Iraqi woman started crying, confiding that she was separated from her boyfriend, a European evacuated from Baghdad one month ago.

Personal dramas unfolded as Baghdadis listened for news from foreign radio stations, such as the Voice of America and the Paris-based Arabic Radio Monte Carlo stations.

Baghdad's main racetrack had kept its gates open Wednesday and although attendance was lower than usual, the bets remained high.

Official Iraqi media remained defiant on the eve of war. If the United States attacked, Iraq "would burn the ground under the feet of the invaders and make them eat the fire," the government newspaper al-Joumhuriya said.

The Iraqi press insisted that Iraq's army was eager for a fight, and threatened the use of unknown, mysterious weapons. If the United States started the war, Iraq "would burn the ground under the feet of the invaders and make them eat the fire," al-Jumhouriya said. It added that Iraq had developed weapons "not known in most military institutions."

"This army is distinguished because it possesses equipment and weaponry about which no one knows anything, except its heroes. Only they know its secrets."