Scores of South Vietnamese were reportedly massing Sunday on both sides of the Cambodian Border. B-52 bombing raids across the frontier has led to speculation that they may soon invade Cambodia to attack North Vietnamese base camps.

B-52 targets in eastern Cambodia included supply lines and base camps above highway seven, about 90 miles north of Saigon, close to where the South Vietnamese troops are believed to be gathering. Field reports indicate that they are preparing to launch attacks on North Vietnamese base camps in order to relieve pressure on Cambodia troops defending the capital of Phnom Penh.

10,000 South Vietnamese Troops

The operations, which may involve as many as 10,000 South Vietnamese troops, will start Monday according to military sources. The troops are expected to concentrate on base areas near Krek and Chup, two towns 60 miles northeast of the capital. The North Vietnamese inflicted heavy casualties on the Cambodian army near highway six last week. The South Vietnamese operation should ameliorate the Cambodian position.

More "protective action" strikes

In other action Sunday, the U.S. Air Force and Navy fighter-bombers made their 79th "protective reaction" strike inside North Vietnam this year. Pilots said they knocked out two enemy anti-aircraft guns 80 miles north of the demilitarized zone.

Other fighter-bombers and B-52 Stratofortresses slammed hundreds of tons of bombs into the underground storage bunkers along the 300-mile Ho Chi Minh trail.

The aim of the air strikes is to slow North Vietnam's annual dry season push of troops and war materials into South Vietnam and Cambodia.