HARARE, ZIMBABWE, JAN. 2 -- One of Zimbabwe's most popular holiday resorts ran an unusual pre-Christmas ad in the Harare newspaper.

"The Chimanimani Hotel is still open," it read. "As the clients have been of late trying to find out about the security position of the place, ALL IS WELL."

The Chimanimani stands less than 10 miles from Zimbabwe's border with Mozambique, and the entire 850-mile frontier is a war zone. Mozambique's 12-year-old guerrilla war has spread into Zimbabwe, bringing almost daily rebel attacks and forcing Zimbabwe to commit already strained resources to a major military effort.

According to Zimbabwe's security minister, Emmerson Mnangagwa, more than 100 Zimbabweans were killed in 1987 in cross-border raids by the Mozambique National Resistance, known by the Portuguese acronym Renamo. The entire 4,000-square-mile Gonarezhou national park on the border has been closed since two park employes and six civilians were killed there in September.

The economic cost of the attacks has not been tallied officially, but glimpses can be found in places like the Chimanimani ad: "For all those who had canceled their bookings, please come and find out for yourselves," it said.

"Renamo has left the interior of Mozambique and {the rebels} are basing themselves along the border, destroying crops and cattle" in Zimbabwe, said Mnangagwa. "There are several incursions a day."

Andrea Chikonye, the 51-year-old foreman at a Marymount mission 10 miles from the border, said in an interview that he lost a daughter, a son-in-law and four grandchildren, ages 1 to 13, in the June 15 attack that marked the beginning of the border war.

After machine-gunning the family members, Chikonye said, guerrillas chopped at their faces with machetes. Observers and government officials here said the rebels sometimes disfigure bodies to make the job of identification all the more gruesome.

The raiders also left a hand-written message amid the blood and burned huts, Chikonye said: "If Mugabe interferes with us, we will interfere with Mugabe."

Mozambique's communist government is on friendly terms with the Marxist president of Zimbabwe, Robert G. Mugabe, but also receives encouragement and support from several western nations, including Britain and the United States. Washington sent $10 million in economic aid and $75 million in food assistance to Mozambique in 1987.

Mugabe has committed 7,000 troops to the fighting in Mozambique. Many of them protect the 180-mile road, rail and pipeline corridor that links landlocked Zimbabwe with the Mozambican port of Beira. But many others fight Renamo elsewhere alongside Mozambique's depleted and disheveled Army.

"The cross-border attacks are plainly some sort of effort to try and get our lot to back off," said David Meltzer, an instructor in the University of Zimbabwe's department of strategic studies. "The {Zimbabwe Army} is hurting {Renamo} far more than the Mozambique troops are."

{Thomas W. Schaaf Jr., a lobbyist for Renamo in Washington, said Saturday that the rebel attacks are "in retaliation for Mugabe's invasion of Mozambique," but denied reports of atrocities allegedly committed by the guerrillas. Mugabe's government is attempting to discredit Renamo, he said, because the rebels have significant support among the population in southeastern Zimbabwe.}

Zimbabwe's crack 6th Brigade, which was trained by the British Army and is 4,000 soldiers strong, has been deployed along the Zimbabwe side of the border. The brigade, which only accepts recruits who have completed the equivalent of their junior year of high school, represents about one-tenth of Zimbabwe's 45,000-man Army.

The war costs Zimbabwe as much as $5 million a month, and the government has been criticized for becoming involved in Mozambique beyond merely protecting Zimbabwe's economic interests. Overall military spending in 1987 consumed nearly one-sixth ($460 million) of Zimbabwe's total $3.1 billion budget.

"If we have to mobilize the entire nation to protect our border, we will do so," Mugabe told reporters in October. "It means diverting our resources. It means tightening our belts."

The Mozambique government sees Renamo's opening of a Zimbabwe front as part of an overall plan by South Africa to destabilize its neighbors. South Africa signed a 1984 agreement to stop supporting Renamo. But weapons and equipment traceable to Pretoria continue to be found near attack sites. Captured guerrillas tell of training at sites inside South Africa, and on Nov. 25 Mozambique's Army overran a Renamo base at Matsequenha, two miles from the South African border. South Africa denies supporting the rebels.

"Pretoria obviously wants to show that it can extend its power," said Carlos Cardoso, director of Mozambique's official news agency. "It also has much to gain by keeping Zimbabwe stuck in a very expensive war."

Mnangagwa said he believes many of the attacks are simply food raids conducted by "desperately hungry" Mozambicans. No one knows how many Mozambicans have fled their destitute homeland for relatively prosperous Zimbabwe, but more than 40,000 of them are jammed into two sprawling camps not far from the Marymount mission.

Hunger may account for many of the attacks, which often involve a raid on a rural store or granary, but it does not explain incidents like the reported Nov. 17 attack on a school near Chipinge, less than 30 miles from the Chimanimani Hotel. There, according to an account by the Zimbabwean government news agency Ziana, guerrillas abducted 20 schoolchildren, killed five and sliced the right ears off another seven. A number of foreign reporters visited the area the following day.

{Schaaf, the Renamo lobbyist, denied that the rebels carried out the raid. He blamed troops of Zimbabwe's 6th Brigade, who he said are trained to stage "pseudo-guerrilla" operations, for the abductions.}

With more than one-quarter of its Army in combat against Renamo, Zimbabwe considers itself at war and does not discuss specific operations. But one military analyst in Harare said he was told that all of Zimbabwe's active-duty troops were stationed along the border during the recent holidays because the mountainous area is a favorite vacation spot.

"Usually soldiers are sent home for Christmas," the source said. "I imagine the Army is going to pay for this later."