Pakistan's army is engaged in fierce fighting for the third consecutive day as it continues its drive against al-Qaeda and Taliban in South Waziristan.
The army has set up five temporary bases in the mountainous region near the Afghan border to try to seal off the Taliban's main stronghold.
There is no clear word about casualties, with each side claiming the other has suffered heavy losses.
Residents in the remote area say dozens of people have died.
Reports from the region are sketchy as it is difficult and dangerous for foreign or Pakistani journalists to operate inside South Waziristan.
At least 20,000 people have fled the area over the last week to the nearby Dera Ismail Khan.
'Consolidating'
Clashes between security forces and the Taliban have continued throughout the night across the South Waziristan region, the BBC's Syed Shoaib Hasan reports from neighbouring Dera Ismail Khan.
But the army has ceased its push into the militant heartland and started to consolidate itself on the periphery before pushing deeper in, our correspondent says.
 | FORCES IN WAZIRISTAN Pakistan army: Two divisions totalling 28,000 soldiers Frontier Corp: Paramilitary forces from tribal areas likely to support army Taliban militants: Estimated between 10,000 and 20,000 Uzbek fighters supporting Taliban: Estimates widely vary between 500-5,000  |
Checkpoints and supply depots have been established in Sherawangai and Mandana in the south-west towards the Tiarza sub-division.
Security forces have used artillery to pound militant positions in Wana, Servakai, Manzai, Jandola and Razmak, in the north, south and east of the area of operations.
Fighter jets have also been deployed to attack the Taliban in Makeen, Nawazkot, Spinkamar, Khaisora and Makeen.
The army has also taken control of the key Ingalmall mountain range, which marks the passage into Afghanistan.
This will play an important role in disrupting the militants' supply lines and in ensuring more help does not arrive from Afghanistan, our correspondent adds.
According to reports, the Taliban have been using heavy weapons to fire back at the troops.
A Taliban spokesman said they had taken dozens of soldiers and not one of their men had been killed.
'Getting nothing'
Meanwhile, hundreds of people from South Waziristan continue to arrive in Dera Ismail Khan to escape fighting.
The BBC's Aleem Maqbool in Dera Ismail Khan says there is very little preparation for the displaced people.
 The army has mobilised artillery and troops in the area |
"At least 20,000 people are registered here. They are not getting anything, some are being taken in by the extended families and relatives," he says.
Meanwhile, the federal government and the military have ordered the closure of educational institutions for a week in Islamabad and some other cities for security reasons.
The closure comes amid fears that militants may try to take hostages to force the authorities to ease pressure on their positions in South Waziristan.
Security is tight across Pakistan and police in Islamabad have searched a number of religious seminaries and some nearby rural areas for militants.
According to reports, nearly a dozen suspects have been detained in a rural locality near the city's main vegetable and fruit market.
Interior Minister Rehman Malik said in a statement that action would be taken against any foreign preachers, if found.
On Sunday, reports said Taliban militants, supported by Uzbek fighters linked to al-Qaeda, were engaged in street clashes with soldiers as the army tried to break the militants' grip on South Waziristan.
An army spokesman said the troops were encountering less resistance than expected but admitted the troops were progressing slowly because of the remote area's rugged, mountainous terrain.
Gen Athar Abbas told the BBC there were mines and IEDs [improvised explosive devices] in the area which required clearance.
The army has been massing troops near the militants' stronghold for months - ever since the governor of Pakistan's North West Frontier Province announced a ground offensive in South Waziristan on 15 June.
Pakistan's government has been under considerable pressure from the US to tackle militancy there.
North and South Waziristan form a lethal militant belt from where insurgents have launched attacks across north-west Pakistan as well as into parts of eastern Afghanistan.
South Waziristan is considered to be the first significant sanctuary for Islamic militants outside Afghanistan since 9/11.
