SANAA, NORTH YEMEN, DEC. 13 -- Senior officials here said political tensions with South Yemen increased today, risking a setback in efforts to normalize relations, after a South Yemeni tribunal sentenced a former president and 34 senior officials to death.

The sentences are the culmination of political purges that swept South Yemen in the wake of a Cabinet-room shootout in the Marxist government between then-president Nasser Mohammed's security forces and rival ministers in January 1986. The factional fighting quickly spilled into the streets, and Mohammed fled to North Yemen. His prime minister, Haider Abu Bakr Attas, succeeded him.

The clashes embarrassed the Soviet Union, which is the principal backer of the ruling Marxist Socialist Party in Aden, and devastated the strategically located seaport capital of South Yemen.

North Yemeni Foreign Minister Abdul Karim Eryani called the year-long trial of 108 former officials a "political" event that was "extremely disappointing" to North Yemen. He said he did not think the sentences would lead to a new round of military tension between the countries, which fought a border war in 1979.

Eryani said his government was "especially disappointed" because the sentences were handed down the day after North Yemeni President Ali Abdullah Saleh had telephoned Aden with an appeal to cancel the trials and release the prisoners, all of whom were charged with high treason, terrorism and sabotage.

"We will continue to do our best to save the lives of the people liable for execution and we hope the international community will do likewise," Eryani said. He said his government would call on the Soviet Union, which has close relations with both Yemens, to seek a stay of any executions.

South Yemeni President Attas must sign death warrants before any executions can take place and officials here suggested that Attas, who presides over a still-divided government, may seek to commute them to avoid international condemnation. International human rights groups recently have expressed concern over reports of torture and summary executions by South Yemen's security forces.

In a separate interview here, South Yemen's former president Mohammed -- who started the shootout last year with an attack on rivals within the ruling party and who was sentenced in absentia yesterday -- warned against executions. "The people of South Yemen are against those sentences," he said, adding that if they are carried out, "such crimes will not pass without punishment."

For the first time since losing power, Mohammed acknowledged in the interview that he bore "collegial responsibility" for igniting the military clash in Aden that resulted in an official death toll of 4,300 people in the street battles that raged for two weeks.

"It is not important to see who began the fighting," he said, adding that the current leadership in Aden "were the ones who really . . . increased tensions."

Of the 64 prisoners present in court for the sentencing, 16 received the maximum penalty of death before a firing squad. Among them were former Air Force chief Ahmed Hussein Mussa and Mubarak Salem, former head of Mohammed's personal security force. Former ministers of power, education and information received sentences ranging from five to 15 years.

Six of the defendants were acquitted, and five people who were tried in absentia were granted amnesty. Charges were dropped against one official who died in prison. Mohammed identified him as Mohammed Ali Muftah.

"We are sure that the reaction of our friends and neighbors will be violent toward those death sentences," said ex-president Mohammed, who had met yesterday with North Yemen's Saleh and Eryani.

Eryani said that some of those sentenced were involved in the violence in Aden last year. "We admit that," he said, "but some of those sitting in judgment were involved, too, and that makes it political."

Some official sources have expressed concern over the refugees who left South Yemen, many of whom live in armed camps just across the North Yemen border. Others have swelled the population of the country's cities. The government has no reliable figures on refugees, and estimates range from 35,000 to 60,000. "Obviously it's an economic drain," said one western official, noting that North Yemen has one of the highest population growth rates in the world.

Mohammed, who met with reporters in a guarded compound near downtown Sanaa, criticized Arab countries of the Persian Gulf, in particular Saudi Arabia, for lending political and financial aid to the Marxist Aden regime and for opposing attempts to unify the two Yemens. "I think Saudi Arabia is gambling with a losing horse, Attas, because I gambled with him -- I made him prime minister -- and I lost," he said.