South Africa arrests key opponents of its new Parliament.

In an apparent display of pre-election nervousness, the South African government has arrested a number of key figures opposed to its plan for bringing Coloreds and Indians into a new-style Parliament.

The arrests - reportedly of Indian, black, and student leaders, including a national president of the United Democratic Front - coincide with the closures of a growing number of schools whose students are disrupting and boycotting classes in opposition to the new Parliament.

Elections for Colored (persons of mixed-race descent) representatives in the Parliament are being held today. The Indian vote will take place on Aug. 28.

Opposition to the Parliament runs deep primarily because it will continue to exclude the country's black majority. Coloreds, and Indians, and whites will occupy separate chambers of the tricameral legislative body, but real power will continue to rest with whites.

Indians and Coloreds who favor participation in the new body say it is a step in the right direction, ending exclusive white rule.

South Africa's white community by and large sees the Parliament as a major concession of political power to nonwhites. The ruling National Party has split over the concept of this ''limited power sharing'' and the government has much at stake in seeing the new political dispensation work.

The government and those favoring participation have been waging an intense campaign for the sympathies of would-be Colored and Indian voters. Those opposed to the new system have urged voters to boycott the elections, hoping that a dismal turnout would discredit the Parliament before it begins. The campaign has turned violent on numerous occasions.

The arrests Tuesday reportedly include key figures from at least five groups favoring an election boycott.

Among those arrested are Archie Gumede, one the United Democratic Front's national presidents, and UDF publicity secretary Patrick Lekota. The UDF, probably the largest anti-election force, was formed a year ago explicitly in opposition to the new Parliament. Most of its members are black.

Top executives of the two most prominent Indian organizations urging voters to boycott have also been detained. They include George Sewpershad, president of the Natal Indian Congress, and Dr. Essop Jassat, president of the Transvaal Indian Congress.

Two other organizations hit by arrests are the South African Students' Association and the Release Mandela Committee, an group pressing for the release from South African prison of African National Congress leader Nelson Mandela. Both groups have urged voters to boycott this week and next week's elections.

The crackdown by the government was presaged by increasingly vehement attacks on pro-boycott groups by government officials and the largely state-controlled television service.

In recent days South African television has attempted to link the UDF with outlawed organizations such as the ANC and the South African Communist Party - links the UDF denies.

Earlier this week the South African minister of law and order, Louis Le Grange, accused the UDF of planning to disrupt the elections ''by means of school boycotts, labor unrest, intimidation, and other acts of violence.''

Also, as a show of opposition to the elections, a number of schools and universities are being boycotted until the elections are over.

According to one estimate, students at at least 44 schools and universities were planning to stay away from classes to show support for an election boycott. A number of schools and universities have already shut down.