Pakistani officials declared today that Thursday's weapons tests established their nation as one of the world's nuclear powers, saying they would not use nuclear arms for offensive purposes but would not hesitate to employ them in response to an attack.

Pakistani Foreign Minister Gohar Ayub Khan said in an interview with the Associated Press that Pakistan is now a nuclear weapons state -- the same declaration that officials in neighboring India made about their nation after exploding five nuclear devices May 11 and 13. Pakistan responded to the tests by India, which has fought -- and won -- three wars with Pakistan in the past 50 years, by announcing Thursday that it had exploded five nuclear devices of its own.

"We have nuclear weapons, we are a nuclear power," Khan said. "We have an advanced missiles program." He added that Pakistan would retaliate "with vengeance and devastating effect" against any attack by India.

Foreign Ministry Secretary Shamshad Ahmad said in a statement that Pakistan had reached the decision to conduct Thursday's test with "a high sense of responsibility."

"Our nuclear weapons capability is solely meant for national self-defense. It will never be used for offensive purposes," the statement said.

The government refused, however, to provide additional details about Thursday's explosions at the Chagai Hills test site in western Pakistan. Prime Minister Nawaz Sharif said Thursday that Pakistan had detonated five nuclear devices, with results "as expected." But the government has not described the types of bombs, nor their sizes and potential yields.

Seismic readings taken outside the country have raised doubts about the size and number of the devices, with some skeptics suggesting that the country claimed five successful tests only to match India's.

Analysts expressed surprise that Pakistan -- estimated to have enough fissionable material for just 15 to 25 bombs -- would use as much as one-third of its nuclear materials on tests, rather than saving them to produce actual weapons.

U.S. satellite images indicate that holes have been drilled and prepared for additional test explosions, intelligence sources said. The government here has refused to rule out the possibility of more tests.

The U.N. Security Council issued a statement today strongly deploring Pakistan's underground nuclear tests and urged both Pakistan and India to refrain from further testing.

Many Pakistanis continued to celebrate their country's technological prowess and defiance of the West -- particularly of the United States, which led the unsuccessful effort to dissuade Pakistan from exploding a nuclear device and now is marshaling efforts to impose economic sanctions on this impoverished country of 135 million people.

"We should bow our heads in humility to Allah for having bestowed us with the wisdom and courage to fight {evil forces}," said a leading conservative daily newspaper, the Muslim, here in the capital. It congratulated Pakistan's military, which runs the country's nuclear program, for having "defied the high priests of the New World Order and secured sovereign deterrence for Pakistan."

But the achievement came at a price that few here expected to pay, though government officials and most Pakistanis interviewed on the street said they were willing to make huge sacrifices to guarantee their security.

"Being a patriotic citizen, if you have to explode a bomb to protect your country and you have to pay a price for it, it doesn't matter," said an official with the Islamabad branch of a Japanese bank who asked not to be identified.

Businessmen, bankers and investors, however, slammed the government's decision to freeze access to their foreign currency accounts as part of a state-of-emergency order announced early today.

The four-month emergency decree was aimed in large part at averting the potential economic crash that analysts say this country may face because of its decision to test. The United States has imposed retaliatory economic sanctions, and other countries are considering cutting off loans and grants and curbing trade with Pakistan.

Many analysts predicted that sanctions could force Pakistan to default on its $50 billion debt, about $32 billion of which is owed to foreign lenders. Pakistan's emergency order freezes about $9 billion in foreign currency now held in private accounts in the country's banking system; those depositors can withdraw the funds only in Pakistani rupees.

In a news conference, Finance Minister Sartaj Aziz said, "The first priority that we have is to safeguard the country's foreign exchange reserves because we need every dollar to meet our country's defense requirements."

Aziz said Pakistan "very reluctantly" froze foreign currency accounts with few exceptions, such as essential travel and the accounts of foreign embassies. The accounts of all others -- foreign or Pakistani, business or individual -- must be withdrawn at the government-set rate of 46 rupees to the dollar. Previously, the rupee was in an unregulated "free float," trading at about 45.80 to the dollar.

"It appears the government has basically decided to {abandon} its drive to turn Pakistan into a truly free-market economy," said the head of an international bank in Pakistan who requested anonymity. "The measures taken on security and the economy in the last 24 hours shatter the prospects for any meaningful local and foreign investments in the country."

Money exchange houses, banks and the Karachi Stock Exchange, which has lost almost a third of its value since India's first test May 11, were closed today. Panicked depositors stormed several bank branches after hearing rumors -- denied by the government -- that safety deposit boxes would be seized.

In addition to foreign companies that tend to want access to their own currencies, millions of Pakistanis traditionally keep accounts in dollars here to hedge against inflation and possible devaluation. About $6.9 billion of the money frozen today is owned by Pakistanis and $2 billion belongs to foreigners, Aziz said.

"This is not a scenario that will make an industrialist happy," said Shoaib Munir, chairman of Sindh Industrial Trading Estate, Pakistan's largest industrial zone. "Industry is bracing itself to go through a rigorous test in the coming months." Anderson reported from Islamabad, Khan from Karachi. CAPTION: Activists from the religious party Jamaat-e-Islami march through Karachi's streets, celebrating the nuclear testing.