Abdul Qadeer Khan

ISLAMABAD, Pakistan (CNN) -- The father of Pakistan's nuclear program, Abdul Qadeer Khan, claimed Saturday his country can mount a nuclear bomb on a medium-range Ghauri missile in a matter of days if the prime minister asks.

"The nuclear devices which we have tested are very compact. They can easily be connected to weapons if the need arises," Khan told CNN. "So we wanted to convey the message that no one should be under any illusion that these are crude and clumsy devices."

"If the prime minister wants it, they can be mounted not in months or weeks, but days," he added.

Khan also described his nuclear program as more sophisticated than India's in an interview published Saturday in Pakistan's leading English-language newspaper, The News. "They have used the old technology of plutonium from spent fuel, whereas we have used enriched uranium, which is much more sophisticated and a safer process," he said.

CNN's Kasra Naji reports from Islamabad, Pakistan 1 min. 50 sec. VXtreme video

The government and public in Pakistan treat Khan as a national hero. He is credited with the design of the Ghauri missile which Pakistan test-fired in April. Khan claims the medium-range missile has a range of nearly 1,000 miles (1,500 kilometers) and can strike any target in India without being detected after firing.

Pakistan tested the Ghauri missile last month

First tests called 'boosted fission devices'

Further details about Thursday's Pakistani tests are reported in the newspaper interview, although they have not been independently confirmed. Khan said those five tests were "all boosted fission devices using uranium 235." He added that Pakistan could conduct a fusion or thermo-nuclear blast "if asked."

He said that of Pakistan's five tests on Thursday, the first was a "big bomb" which had a yield of about 30-25 kilotons. Most estimates by outsiders have been considerably lower.

"The other four were small tactical weapons of low yield. Tipped on small missiles, they can be used in the battlefield against concentrations of troops," he told the newspaper.

"None of these (five) explosions were thermo-nuclear. We are doing research and can do a fusion blast. If asked. But it depends on the circumstances, political situation and the decision of the government," he said.

Public celebrates Khan as a national hero

The number and strength of Thursday's tests have not been confirmed by sources outside Islamabad, and some experts have told CNN that Pakistan may not have exploded five devices on Thursday. Evidence from monitoring stations outside Pakistan suggests there was only one seismic event.

On Saturday, Pakistani media originally reported that two devices were tested, but Shamshad Ahmed Khan of the Foreign Ministry said in Pakistan's formal announcement only one device was tested.

In the newspaper interview, conducted before Pakistan tested again Saturday, Khan was asked how many nuclear weapons India had. He said, "The numbers are less important than their effectiveness and sophistication."

"If there is a war, you need only a few. Deterrence is the main advantage. Now they (India) know we also have nuclear weapons, they will think 10 times before invading us."

Reporter Kasra Naji andReuters contributed to this report.