Islamabad, Pakistan (CNN) -- Pakistani security forces shelled Taliban strongholds in northwest Pakistan on Monday, killing 21 alleged militants and injuring at least 30 others, a top government official in the region told CNN.
Ground troops and helicopter gunships attacked alleged militant hideouts in Mohmand, one of seven districts in Pakistan's tribal region along the border with Afghanistan, said Maqsood Amin.
CNN could not independently verify the account or the death toll because access to Mohmand and the rest of the tribal region is severely restricted.
Mohmand is believed to be a hideout for Taliban fighters and al Qaeda-linked militants fleeing last year's military operation in the district of South Waziristan and ongoing U.S. drone strikes in North Waziristan.
The Pakistani army has carried out numerous ground and air operations in Mohmand, but hasn't been able to stamp out the militants.
In December, 11 Pakistani soldiers were killed when about 150 militants ambushed six security checkpoints in Mohmand, officials told CNN.
Earlier in December, a twin suicide attack targeting a government building in Mohmand killed at least 40 people.