JAKARTA, Indonesia (AP) _ Rioters tore through the smoke-filled Indonesian capital Thursday, burning and looting in the worst violence in decades and the biggest challenge yet to President Suharto's rule. With 20 reported killed, the military ordered its troops to take over the streets.

Tanks rolled through the streets in a show of force during a third straight day of arson, looting and gunfire.

Plumes of thick smoke billowed across the skyline of Jakarta. Mobs set afire cars, tires, shops and houses. Rock-throwing teens and children smashed hundreds of windows in a frenzy of destruction that sent foreigners fleeing.

``Jakarta is on fire. We'll go anywhere,'' said Siaumei Wen, a 27-year-old Chinese woman trying to buy plane tickets out for her family.

The violence erupted when police shot to death six student marchers Tuesday, after tolerating three months of intensifying protests over an economic crisis that has sent prices and unemployment soaring.

Unconfirmed reports said as many as 20 people were dead or missing and feared dead Thursday. The military said four soldiers were also killed.

``We must face rioters and looters firmly. We are soldiers who will support the nation and we will never surrender,'' Maj. Gen. Syafrie Syamsudin, the city's military commander, said in an evening speech to troops that was broadcast on local television. Witnesses said security forces resorted to firing directly into crowds to try to clear the streets.

Frightened residents complained the military failed to stop mobs rampaging through many parts of the city. In some places, the crowds cheered the troops and clambered aboard their vehicles as soldiers stood by, sometimes chatting with protesters.

``As good citizens, we have to work together for reform. Let's not fight each other,'' one soldier shouted through a loudspeaker.

The rioting paralyzed the capital of 11 million people, and raised doubts about the political future of the world's fourth most-populous nation.

Armored personnel carriers were positioned around the city, including three outside the U.S. Embassy, which urged Americans to defer nonessential travel to Indonesia and decided to evacuate relatives of embassy staff. Some U.S., Japanese and other foreign companies temporarily closed offices and ordered employees home.

Syamsudin's crackdown orders came as Suharto, Asia's longest ruling leader, cut short a visit to Egypt. He headed home to save an authoritarian regime seemingly more dependent than ever on the military's support during the country's worst economic turmoil in three decades.

Syamsudin made no direct reference to the president but said the 10,000 soldiers deployed across Jakarta ``will obey our leadership.''

Suharto, a 76-year-old retired army general, used the might of the army to grab power amid social and economic turmoil 32 years ago. He has cracked down ruthlessly on critics over the years to keep opposition groups weak.

Newspapers carried reports quoting Suharto as saying he was willing step down if people no longer trusted him. Lawmakers said they would discuss the issue next week.

But Foreign Minister Ali Alatas played down the possibility, saying Suharto could be replaced only through a lengthy constitutional process.

The unrest exploded last week after Suharto introduced new austerity measures under a $43 billion rescue plan imposed by the International Monetary Fund.

Looters acted largely out of anger over rising food prices and reduced subsidies on fuel, transport and electricity.

``Very good, very good,'' looters chanted as they rushed from store to store, burning and stealing. Crowds of onlookers, mostly men, cheered.

Many of the shops looted Thursday belonged to ethnic Chinese, a small minority of Indonesia's 200 million population who dominate commerce and have been made scapegoats during the economic crisis.

Dozens of Chinese headed to the airport for flights out of the capital. Many who could not get a plane seat abandoned their houses and booked into five-star hotels that had beefed-up security.

The house of Indonesia's richest man, Liem Soei Liong, an ethnic Chinese billionaire with close links to Suharto, was trashed and burned. The headquarters of the Social Affairs Department, headed by Suharto's oldest daughter, also was gutted by fire.

Elsewhere, rioters burned a police station, while officers fired at them and a helicopter dropped tear gas canisters.

In Washington, the Clinton administration delayed sending a top military officer to Indonesia to urge its leaders to use restraint in dealing with rioting.

The postponement was prompted by the deteriorating situation in Jakarta, said Stanley Roth, an assistant secretary of state.