CALCUTTA, India (AP) _ A demonstration by 250,000 Indians to mark the anniversary of the Hiroshima bombing signaled that initial euphoria over India's nuclear tests is waning amid heightened tensions with Pakistan.

The demonstrators jammed the streets of Calcutta on Thursday _ the world's largest gathering to mark the day the first atomic bomb was dropped _ to show they don't want a similar tragedy to befall South Asia.

The huge protest contrasted with the initial rush of nationalist pride in May, when Indians celebrated exuberantly in the streets after the test blasts.

``We don't want the bomb! We want peace!'' the crowd chanted Thursday in a Calcutta stadium. Celebrities and writers joined a throng of factory workers and students in a three-mile march.

Smaller anti-nuclear demonstrations were held throughout India. ``Bread, not bombs!'' shouted demonstrators in New Delhi, where spiraling food prices and electricity shortages have dampened enthusiasm over the nuclear tests.

In Hiroshima, Japan, 50,000 people clasped hands in prayer and observed a moment of silence at 8:15 a.m. _ the exact time the United States dropped the bomb that devastated their city Aug. 6, 1945.

Peace activists in Oak Ridge, Tenn., marked the anniversary with a demonstration outside the Y-12 nuclear weapons plant that supplied uranium for the bomb.

In Pakistan, which followed India into the nuclear age with tests of its own, a few hundred people held protests in the three largest cities, Islamabad, Lahore and Karachi.

The smaller size of the demonstrations reflected most Pakistanis' belief that a nuclear bomb is their only defense against their more powerful rival.

The rivalry between Pakistan and India has led to three wars in the past 50 years, and the subcontinent is considered the world's most likely nuclear flashpoint. Two of the three wars have been over the disputed Himalayan region of Kashmir.