The insurgent Western Somali Liberation Front has clearly demonstrated that it now controls a large slice of Ethiopia's Ogaden region and enjoys widespread popular support.

In a five-day trip over nearly 500 miles of sandy Ogaden roads and bush tracks, a group of Western journalists, who were accompanied by a Somali Foreign Ministry official, never saw any trace of Ethiopian soldiers, whose former haunts are now patrolled around the clock by Somalis.

Although the excusion through the southern reaches of Ethiopia's semiarid Hararghe region touched on only 10 or 20 per cent of the Ethiopian territory the Somalis now refer to as "western Somalia," the Front claims that the area is representative of the control it exercises over almost the whole region, nearly a third of Ethiopia.

The journalists never ventured more than 150 miles from the Somali border, but the claim seems plausible.

The Front's leaders say that Ethiopian troops in the region are now confined to the besieged cities of Dire Dawa, Harrar, and Jijiga in the north and Negele in the south. This is confirmed by diplomatic sources in both Addis Ababa and Mogadishu.

Certainly the sic former Ethiopian garrisons we visited, which until last month housed some 8,000 soldiers, are under Somali control.

The Front's well-coordinated attack began July 12. Military officials of the Front say that plans for the attacks began two years ago, when they began stokpiling arms in the Ogaden hills, but that it was not until June 14 that specific dates for the attacks were decided.

The insurgents have refused to reveal the overall strength of their forces, but they claim to have outnumbered the Ethiopian adversaries handsomely in every confrontation. The Front says that hundreds of Ethiopians at Mustahil, Kelafo, Gode and Werder were killed and about 2,000 were taken prisoner.But they are rarely prepared to enumerate their own casualties.

None of the captured Ethiopians were seen by reporters, but the Front says they are geing humanely treated in POW camps within the occupied area.

However, nine Ethiopians who escaped during or after the 12-day battle of Gode, which ended July 24, and who were captured during the past week by well-armed Somali 'Nomads in the surrounding hills, were seen by the journalists.

Nereyo Berey, 25, a farmer from Ethiopia's northern Tigre region, said he was abducted from his home into Ethiopia's militia, given three months den , was the only place the journalists visted where Ethiopian soldiers were reinforced by militiament. There were reinforced by militiamen. There were signs of fierce fighting and material destruction caused by heavy weapons in Werder, Mustahil and Kelafo.

In all of those places there were destroyed buildings and vehicles, ashes and rubble and shells and casings for artillery ammunition.

In Gode there were several Ethiopian bodies lying in ditches, but the Somalis said they had been buried and uncovered by carnvivorous wild animals.

The front commanders at Ferfer and Burukur, which had garrisons of 300 and 120 Ethiopians respectively, said the soldiers ran away without fighting. At Ferfer some Ethiopian prisoners were captured.

In every locality the journalists visited, the Front organized demonstrations of up to 500 people who emotionally pledged their support to Somalia and chanted incessantly "Down with Mengistu." Almost all the adults at the demonstrations were armed, with anything from AK-47 automatice rifles to bows and arrows.

It is unlikely that the Ethiopian government will accept their territorial losses as permanent. It seems equally improbable that they will soon be in a position to reconquer the area.

The military structure the Ethiopians built up during the past 29 years to hold the area has been completely of military training and flown to Gode.

Gode, said to be the scene of the fiercest battle in the southern Ogadestroyed, and huge stockpiles of arms and ammunition - much of it American-made - have fallen into the Front's hands. Front officers now ride around Gode and Werder in American Jeeps, and Gode's mile-and-a-half-long paved runway is protected by Front soldiers manning American antiaircraft guns.

Even without the captured equipment, the Front hardly seems poorly equipped. Bashir Mohamed, the Front's political commissioner for Kelafo, said his troops were just as well armed as the Ethiopians during the seven-day battle that ended July 26 with the fall of Kelafo.

The Somali civilians, who claim to be Front irregular insurgents, are also well armed. Some young women dressed incongruously in elegant flowing Somali dresses brandished AK-47 automatic rifles at the demonstrations and claimed to have used them during the battles.

According to Front leaders, their aims is to first capture the four towns in the area still under Ethiopian control and then decide on their political future.

According to candid Somalis, this will amost certainly be a complete merger with Somalia.

According to the Ethiopians, the Front itself is a Somali government creation. But the Somalis say the organization grew out of the Somali freedom movement, with antecedents dating back to the early part of the century when Mohammed Abdulla Ahassan led Somali legions against the British, Italians and Ethiopians.

The Front, however, did a thorough if not totally convincing job of maintaining the charade that it receives no military assistance from Somalia.

Ali Ahmed, a senior Front official, admitted that some former Somali soldiers have joined the insurgents and that Front men have trained with the Somali army.

Although no activa Somali Republic units were visible in the area, the insurgent forces wore khaki uniforms identical to the one worn by Ahmed Mohammed Ali, a POW whom Ethiopian authorities showed to Western journalists 10 days ago and who was a regular Somali soldier fighting in Ethiopia.

There was no evidence of Somali planes or tanks in the region, but on the Somali side of the frontier there were two tanks immobilized and ditches, suggesting that other tanks may have previously crossed the border.

Whatever the extent of Somali Republic involvement in the Ogaden war, the Somali people of the Ogaden seem exuberant that the Ethiopians have been dislodged from the huge area.