Baluchistan province

ISLAMABAD, Pakistan (CNN) -- Pakistan detonated one more nuclear device Saturday in the remote southwest, defying international calls to halt further tests and further escalating the nuclear arms race in South Asia.

Earlier reports had suggested that Pakistan had exploded two nuclear devices Saturday. The latest nuclear detonation follows Pakistan's tests of five nuclear devices on Thursday, in response to rival India's nuclear tests earlier this month.

Foreign Minister Gohar Ayub Khan said the test was carried out in the remote hills of the southwestern province of Baluchistan near the Thursday test site, about 700 miles (1120 km) southwest of Islamabad.

Asked if more nuclear tests were carried out on Saturday, Khan told Reuters: "Yes, by the grace of God."

Foreign Minister Gohar Ayub Khan

There were conflicting reports as to the strength of the detonation. Sources at Pakistan's Kahuta Research Laboratories described the test to CNN as relatively small. But other reports suggested it was more powerful than Thursday's tests.

Pakistani Prime Minister Nawaz Sharif is to travel later Saturday to Lahore, the capital of Pakistan's Punjab province, where he plans to hold a news conference. The last time Sharif appeared publicly was on national television Thursday to announce nuclear tests had been conducted.

In an interview with CNN Friday, Khan said Pakistan's nuclear program was active and did not rule out further tests.

Saturday's test brings to six the number of nuclear tests Pakistan has conducted. India also has conducted six tests since 1974. Pakistan's most recent test raises fears that tensions in the region could spiral into a nuclear conflict.

Pakistani Prime Minister Nawaz Sharif

Britain condemned Saturday's test saying Pakistan is acting irresponsible and in defiance of international opinion. British Foreign Secretary Robin Cook said the test does "nothing to enhance Pakistan's security environment. (It) further escalates tensions and heightens concerns about an arms race in South Asia."

Britain said on Friday that it is withdrawing its ambassador to Pakistan and will likely impose sanctions.

A Japan news agency reported that Japan may recall its ambassador to Pakistan in response to the country's latest nuclear test.

On Friday, the Security Council declared in a statement that it deplored the tests and urged Pakistan and India to refrain from further testing and sign nuclear arms control treaties -- unconditionally and immediately.

The United States hopes to follow the declaration with a meeting of the foreign ministers of the five permanent members -- the United States, Russia, China, Britain and France -- to discuss further steps to curb the nuclear arms race in South Asia.