Demonstrators demanding the resignation - and even the life - of Prime Minister Zulfiqar Ali Bhutto defied the first day of martial law regulations here and marched through the city's streets today. Armed troops and police killed 11 of them.

In other turbulent Pakistani cities, at least 10 demonstrators were shot to death by police and gunmen of Bhutto's ruling party. Between 60 and 80 persons were wounded throughout the country. At least four persons were killed in the Northwest Frontier Province capital Peshawar, which had been calm until today.

A general strike called by the opposition was observed in major cities. Together with martial law curfews, the strike brought economic life to a standstill in several regions.

(UPI reported that the border with India was closed at Lahore. A border official said he was ordered "even to turn ambassadors back.")

In the national capital, Islamabad, the beleaguered prime minister met with members of Parliament from his Pakistan People's Party to explain his plans and his reasons for imposing martial law last night in three cities. Reports from the capital indicated that Bhutto won the legislator's support.

Observers here interpreted this as a hardening of the prime minister's stance against spreading popular opposition to his rule.

The six-week-old campaign to oust Bhutto began after he was returned to office in elections last month that were widely believed to be rigged.

The emergence of the army, with shoot-to-kill orders, to try to put down the protests has caused popular resentment of the military, a new development in the unrest here. Until now, the protesting workers have reserved their hatred for the police, and the army generally has been credited with striving to maintain calm.

Bloodshed in the Liaquatabad area of Karachi, a hotbed of opposition to the prime minister, especially seemed to turn public opinion against the army. Seven persons were killed there today.

"Now our prime minister has unleashed the army on us," said an iron-worker who identified himself as Hanif Abdullah. "If he wants to kill us so badly, then his means that he considers us his enemies. So it is war and we demand Mr. Bhutto's life in return."

Abdullah spoke as he showed a foreigner pools of blood at the entrance to a dusty alley leading into Liaquatabad's main business street. Just a few minutes earlier, armed troops and police had halted a procession of 2,000 men and boys pouring out of a nearby mosque.

"Without warning," Abdullah said, "they suddenly turned their rifles on us and opened fire." He said that although the army officer in charge of the troops had ordered his men to fire at the legs of the demonstrators several young boys had been hit in the chest and head.

Seven men and boys died in the gunfire and an estimated 30 were wounded, some of them seriously. All the victims were immediately rushed off by police in a comandeered truck to a hospital, where officials confirmed the casualty figures.

As Abdullah spoke, another truck filled with troops wearing camouflage tunics and Workd War I vintage helmets rumbled past. A roar went up from the crowd: "Death to the Pakistan Army."

Meanwhile, leaders of the nine-party opposition political front, the Pakistan National Alliance, and the 26-union Pakistan Labor Alliance, which organized a nationwide strike now in its third day, insisted that they had no intention of backing down.

Mohammed Sharif, president of the Labor Alliance, said the workers considered martial law "unacceptable.

"This strike proves beyond all doubt that the people of Pakistan do not support Mr. Bhutto," he said in an interview. "We will not call it off until he steps down and calls for fresh elections."

Martial law, imposed last night in Karachi, Lahore and Hyderabad, and a curfew which was extended today to the Punjab industrial city of Lyallpur, have taken the initiative away from the strikers. Since the curfew keeps industry paralyzed, however, the net effect is the same.

Whether industry is crippled by strike or martial law, the question that remains, is how long Bhutto can afford to sacrifice this impoverished nation's economy to stay in power. A western economist in Karachi, which generates more than half of the nation's industrial income, noted that Pakistan is already $6 billion in debt to foreign governments.

Economic pressure is mounting on poor workers, most of whom lead a hand-to-mouth existence with small daily wages. Yet, few if any seem sufficiently disturbed to consider relenting on the issue of Bhutto, who has become a hated figure.

"This is a very bad sign," a top ranking army officer said when a journalist informed him of the Liaqatabad incident. "I know for a fact that our boys die inside themselves when they must fire on their own people."

Earlier in the day, during the 12-to-4 p.m. period when the curfew was lifted to allow people to shop for food, a group of workmen in the congested Burns Road section of Karachi said they would be willing to accept martial law as long as it was not identified with Bhutto and as long as it was clear that the army would quickly oversee new general elections.

As the baking heat of the day wore on, and news of the killings at Liaquatabad spread along the grapevine and on wall posters, this attitude changed drastically. "Our army surrenders to the enemy but fires on our own defenseless peoples," a white-bearded elder said.

He was referring to the surrender of the Pakistan army to India in December 1971, when Pakistan lost its eastern wing, which became Bangladesh. For several years afterward, the army was in disgrace. Its fortunes began to change recently, but military involvement against the protests may reverse that trend.

A retired senior army officer, who maintains close contact with military units in Karachi, said tonight he believed the Liaquatabad incident was the result of poor judgment by an exhausted officer. "You must remember that these boys are spread thin on the ground. Many of them have been on 24-hour duty for more than a fortnight now," he said.

The retired officer said that he perceived "cracks" in the ranks of the army. "There's no doubt that the top brass support Mr. Bhutto," he said. "After all, he's handpicked them, in many cases promoting them over the heads of more senior officers, but the field grade officers and the enlisted men are the ones who have to point their weapons at their own people. Its's a terrible thing for any soldier."

[Manchester Guardian correspondent Walter Schwarz reported from Rawalpindi that efforts will be made next week to persuade people to go back to work. Officials said that factories in Karachi will reopen, and under martial law provisions, workers who do not report for work will be summarily dismissed.]