The pullout, announced by Singh, is part of India's plan to reduce the number of troops fighting the 16-year-old rebellion by Muslim separatists.
A senior army officer said the troops would be "de-inducted" from various parts of Indian-administered Kashmir including Anantnag, its second largest town, 55km south of Srinagar.
Lieutenant General Nirbhay Sharma, commander of army's 15 Corps, told a news conference late on Tuesday that operational details were still being finalised.
"I can’t tell you how many troops are being de-inducted," he said.
"The de-induction of the first batch of troops is taking place keeping in view the operational requirement."
He said the military situation in the region had improved and that the infiltration of separatist fighters from across the Line of Control in his area of operation had been reduced in the recent months.
Singh is on a two-day visit to
Kashmir on 17 November
Agencies have reported that 20,000 soldiers will be pulled from Indian-administered Kashmir. Military estimates place the total number of soldiers in the state at about 250,000.
"They will now serve outside Jammu and Kashmir," Lt Gen Sharma said.
The pullout is to be followed by political and economic concessions for the state expected to be announced during Singh's two-day visit starting on Wednesday.
Meanwhile, Kashmir's chief Muslim cleric, Mirwaiz Umar Farooq, who also heads the moderate faction of the Hurriyat Conference, said on Tuesday that he and his colleagues would hold talks with Singh only after being allowed to travel to Pakistan.
"The de-induction of the first batch of troops is taking place keeping in view the operational requirement"
Lieutenant General Nirbhay Sharma, commander
Farooq was earlier quoted by the Indian media as saying he had agreed to meet the Indian prime minister during his visit, a claim he later denied.
"No such decision has been taken by the Hurriyat Conference," the cleric-politician told Aljazeera.net.
He confirmed reports that he and other Hurriyat Conference leaders would apply to the Indian government for travel documents for their visit to Pakistan.
"They [Indian officials] have said the government is not averse to our visiting Pakistan and that we should go through the proper method to get the travel documents for that. We are doing it," he said.
Farooq, who has already held two rounds of talks with New Delhi, said if the Indian government allowed him and his colleagues to travel to Pakistan further talks were likely.
"We shall on our return hold the third rounds of talks with the prime minister and other prominent Indian political leaders," he said.