By Paul Anderson
BBC correspondent in Islamabad
Military officials in Pakistan say there has been a fresh attack by Islamic militants on a military camp in the troubled area of South Waziristan.
The military have been accused of not admitting true casualty figures
There has been no word so far on the latest casualties.
The attack follows clashes on Wednesday between militants and Pakistani security forces in which the army said 20 militants were killed.
The escalation of violence in the area comes after tribal militias came under pressure to capture militants.
Militants attacked the camp in Wana, the main town in South Waziristan, in the early hours of Thursday morning using rockets and small arms.
The ensuing exchange of rocket, mortar and gunfire lasted around an hour.
There were no reports of casualties.
Clashes on Wednesday in a different part of the South Waziristan agency left at least 24 people dead.
According to officials, most of them were foreign Islamic militants suspected of having links to al-Qaeda.
However, Pakistan's media are challenging those figures, saying the security forces suffered far higher casualties.
Reports from unidentified security sources in Wana speak of the death of up to 13 military personnel.
The question now is whether the renewed violence will push the army into launching another operation against hundreds of militants and the tribesmen who have been protecting them.
In March more than 120 people were killed, many of them military as well as militants, in the biggest operation launched by the army to sweep up al-Qaeda suspects.
That was deemed a failure and the army switched to softer tactics, trying to persuade tribes people to hand over foreigners for registration.
So far not a single militant has surrendered.