MADRID, Spain (AP) _ The Guardia Civil, in his gray-green uniform and tricorne hat of black patent leather, personifies the law in Spain and is a prime target of Basque separatist guerrillas.

Nine more of the paramilitary civil guards died Monday in a car bomb attack on a bus and van carrying young officers to a training center. That brought to 164 the number of men lost to terrorist attacks since 1968 by the corps that was nicknamed ''the well-appreciated'' when it was founded in 1844.

Police and government officials believe Monday's bombing was the work of the ''Spain Commando'' of the Basque separatist organization ETA.

When guerrillas of the ETA, initials of the words Basque Land and Liberty in the Basque language, began its campaign against the dictatorship of Gen. Francisco Franco in 1968, they concentrated on the civil guards.

Representative government was restored after Franco's death in 1975 and general elections two years later, but the ETA continued killing civil guards, other policemen and military officers in its attempt to win independence for northern Spain's three Basque provinces.

On Feb. 23, 1981, more than 100 civil guards led by Lt. Col. Antonio Tejero took over Parliament at gunpoint, holding the entire lower house hostage for more than 18 hours in a coup attempt that failed when King Juan Carlos went on nationwide television to support the new democratic government.

The Guardia Civil is part of the army and is led by a military officer, currently Lt. Gen. Jose Antonio Saenz de Santamaria.

Although there have been calls to separate the corps from the army under recent legislation modifying the security forces, Defense Minister Narcis Serra has insisted on keeping the civil guards in the military structure.

During the reign of Queen Isabela II, the War Ministry established the civil guard to patrol the vast Spanish countryside and control bandits and anti-royalist factions.

Pairs of officers, mounted on horseback or walking along rural roads, served as reminders that the government in Madrid was determined to keep the rest of the country in hand.

In addition to patrolling rural areas, the civil guard now serves as a national highway police force, has special anti-terrorist units and guards all important government buildings and foreign embassies.

From the beginning, the rule has been for civil guards to serve outside their home regions and live with their families in barracks set apart from the residents of the towns in which their posts are located.

ETA demands that the central government remove the civil guards, which it calls an army of occupation, from the Basque provinces.

The Guardia Civil now employs psychiatrists to help its personnel and their families stationed in the Basque country to cope with community rejection and the constant fear of attack.