Pakistan's military says security forces have killed 19 "terrorists" during a ground operation in a northwestern tribal region near the Afghan border.

It says four troops were killed in Saturday's fighting in the Shawal area of North Waziristan. It says "several" militants were wounded during the final phase of the operation, which was launched earlier this week.

Pakistan has been waging a military offensive against militants in North Waziristan since June 2014. The army says it has killed around 3,500 insurgents since then.

The rugged region has long been a stronghold for the Taliban, al-Qaida and other militants, who launch attacks on both sides of the porous border.