By Jonathan Head
BBC News, Bangkok
The request by the government of East Timor for international military help to restore order is a serious setback for the country, just a year after the last international peacekeeping force departed.
Security forces have failed to quell the violence
Left in ruins by rampaging Indonesian troops in 1999, East Timor was administered directly by a United Nations mission for the following three years, and was widely viewed as a UN success story.
But in recent weeks there has been gunfire in the streets of the capital, Dili and in the hills outside, gangs have clashed and torched buildings and cars.
East Timor was supposed to have left such scenes in its past.
Most alarmingly, they involve rival units of the country's young army, and occasionally its police force.
Critics of the United Nations mission in East Timor complained long ago that the army was created in too much haste. Key jobs went to the commanders of the armed resistance force, Falintil, and their followers.
Many who considered themselves veterans of the independence struggle were left out, and have continued to agitate for compensation, sometimes stirring up gangs of youths into occasional rioting.
Feb: More than 400 troops strike over pay and conditions
March: Government sacks nearly 600 of 1,400-man army
April: Rioting by sacked troops leaves five people dead
At such times the police force has proved unable to maintain order.
Many in its ranks lack basic policing skills. A core contingent which does have experience from the Indonesian police is resented by the rest.
These weaknesses in East Timor's two security forces have been compounded by many other factors.
Rival members of the governing Fretilin party are believed to be stirring up discontented troops.
Furthermore, Prime Minister Mari Alkitiri and other ministers who spent the 24-year Indonesian occupation in exile lack popular support.
And most of all, chronic poverty and unemployment still afflicts most of the population.
Significant revenue from East Timor's offshore oil is now starting to arrive.
But in the current climate, there is a real risk that rivalry for those funds may provoke further instability in the lead up to next year's general election - the first since East Timor declared independence in 2002.