Speaking after receiving the petition on behalf of the Army Area 3 commander, Maj-General Suppha-aksorn Sangprakul said the construction of Route 121 had not received approval from the Army.

The 10.5km road encroaches on areas belonging to two local Army units as well as the national park.

The officer said the Army's Area 3 commanders had told the Highway Department not to build the road on Army property, but the construction had continued.

Professor Chalermphol Samphet, a leader of the "Lovers of Chiang Mai" group, said the Highway Department had begun work without either the mandatory environmental-impact assessment (EIA) or staging a public forum.

A source said the road was part of a new network which involved Route 1017 (Bo Sang-Doi Saket) and Route 11 (Chiang Mai airport-Rin Kham Intersection) which was initiated after Prime Minister Thaksin Shinawatra undertook an aerial inspection last June.

There are plans to build a golf course inside the national park after Route 121 is completed.

The source said a number of Army officers who were classmates of Thaksin during military school had been approached to convince the prime minister to "quell" local residents' opposition to the Route 121 project.

The Bt513-million construction contract has allegedly been awarded to a company owned by the father-in-law of a minister close to Thaksin.