PORT MORESBY, Oct 1 Papua New Guinea's defence chief said today the army had no plans to

PORT MORESBY, Oct 1 (Reuters) Papua New Guinea's defence chief said today the army had no plans to arrest Prime Minister Michael Somare when he returns home and charge him with treason.

The Papua New Guinea (PNG) police force said, however, it had heightened security ahead of Somare's expected return tomorrow, after attending the UN General Assembly meeting in New York.

Somare had been due to arrive home today, but is believed to still be in Singapore.

Defence Force Commander Peter Ilau said civilians were spreading rumours that the military would arrest Somare when he returned to the capital Port Moresby.

''I can assure you that whoever is spreading the rumour -- the rumour is coming from outside, from the civil street,'' Ilau told a news conference in the capital.

''There is no involvement by the military,'' he said.

The Post Courier, one of the nation's two major newspapers, reported today the military would arrest Somare over the escape from PNG of an alleged child sex offender.

Lawyer Julian Moti is wanted by Australian authorities to face charges he raped a 13-year-old girl in Vanuatu in 1997.

Moti, now the attorney general in the neighbouring Solomon Islands, was secretly flown out of PNG on a military aircaft in 2006, avoiding extradition to Australia.

A PNG defence force report into Moti's escape to the Solomons found Somare and others had been involved and that charges should be laid, the Post Courier said.

The Moti affair severely damaged diplomatic relations between Australia and its two South Pacific neighbours.

Somare has denied any involvement and has said he would legally challenge the defence report, which is now in the hands of PNG's defence minister.

PNG Police Commissioner Gari Baki said today that police had for two weeks been monitoring rumours that disgruntled soldiers were about to arrest Somare.

''At this point in time, it's still a rumour, but we are not taking any chances on that,'' Baki told reporters.

Baki said extra security would be provided for Somare when he returned.

Somare, 71, is known as ''the Chief'' in PNG which he led to independence in 1975. He is in his fourth term as prime minister, having won a second straight term in August, promising to help Pacific neighbours stand up for their sovereignty.

PNG is a nation of about 6 million people. Despite its vast mineral resources, most people lead subsistence lives in villages, with about 40 percent living on less than $1 a day.

REUTERS SKB HS1517