A suspected U.S. missile strike killed at least 13 people Sunday in a tribal region where Pakistan's top Taliban commander is based, intelligence officials said, breaking a lull in such attacks and posing a test for growing anti-Taliban sentiment in the country.

The strike came as violence raged elsewhere in the volatile northwest region bordering Afghanistan: a bombing at a market killed at least eight people, while officials said clashes between the Taliban and security forces killed at least 20 militants in a tribal region supposedly cleared of insurgents months ago.

Local media have reported that the Taliban claimed responsibility for several recent attacks in Pakistan, including one that killed a moderate cleric, calling them revenge for the army's offensive in the northwestern Swat Valley.

The attacks seem to have bolstered growing anti-Taliban sentiment in Pakistan, something the U.S. hopes will translate into support for sustained military action against extremists who use Pakistani soil to plot attacks on Western troops in Afghanistan.

But U.S. missile strikes could undermine that sentiment because they are deeply unpopular among Pakistanis. The government has publicly protested such strikes, fired by unmanned drone aircraft, saying they violate the country's sovereignty, even though many analysts suspect the two countries have struck a secret deal to facilitate the attacks.

The U.S. rarely acknowledges or discusses the missile strikes.

The latest strike — the first since mid-May — occurred in South Waziristan, hitting three vehicles in an area not far from Makeen, a village considered a stronghold of Pakistani Taliban chief Baitullah Mehsud. It was not clear who the five people killed were. Two Pakistani intelligence officials confirmed the attack on condition of anonymity because they were not authorized to speak to media.

South Waziristan, which also is an Al Qaeda stronghold, is believed to be the target of Pakistan's next offensive against militants. Mehsud has been linked to bombings on both sides of the Afghanistan-Pakistan border, and U.S. defense officials said last week that Pakistan intends to go after him, though no timeframe was given.

In recent weeks, militants and security forces have repeatedly skirmished in South Waziristan, though the army insists it is merely responding to attacks.

In a statement, the army said it killed some 30 militants in South Waziristan in Saturday strikes aimed in part at avenging the death of cleric Sarfraz Naeemi. Naeemi, killed in a suicide bombing Friday, had denounced the Taliban as murderers.

The market bombing Sunday occurred in Dera Ismail Khan, a town not far from South Waziristan.

Government official Inayat Ullah said 11 to 13 pounds of explosives were planted in a fruit vendor's hand-pulled cart. Police official Mohammad Iqbal put the death toll at eight, with 20 wounded.

At a hospital where some of the wounded were taken, wails and cries filled the air.

"It was crowded there when something big exploded," said 30-year-old Ilyas Ahmad, whose legs were wounded. "It was a big noise. Everybody was crying. Bodies were lying there. People were lying around blood."

Iqbal said the attack had to be a response to the Swat operation. On Saturday, senior provincial minister Bashir Bilour said the latest attacks could also be the work of militants in Waziristan ahead of "an imminent army operation" in the region.

Fighting on too many fronts could tax Pakistan's military, not to mention government resources. The latest clashes in the Bajur tribal region underscore the challenges facing the military in holding territory it claims to have cleared.

Pakistani security forces used jets, helicopters and artillery to pound suspected Taliban hideouts in Bajur over the weekend.

Zakir Hussain Afridi, the top government official for Bajur, said the fighting was in the Charmang valley, a stretch he described as largely under Taliban control. Jamil Khan, his deputy, put the militant death toll at 20 since Friday.

Bajur was the main theater of operations against the militants before Swat. After some six months of fighting, the army said in February that the Taliban there had been defeated. But reports have occasionally surfaced since then of ongoing militant activity.

Afridi told The Associated Press that the military had used airstrikes in the past in Charmang but that there were no ground troops — army or paramilitary — in that part of Bajur.

Pakistan had relied heavily on local tribes in Bajur to raise their own militias to force out local Taliban, but Afridi said that concept had not taken off well in Charmang.

Military officials could not immediately be reached for comment Sunday.

The military says its operation dating to late April has killed more than 1,300 militants in Swat and surrounding areas. But the Swat offensive has already displaced more than 2 million civilians, a huge humanitarian test for Pakistan. More battles along the Afghan border could swell that number.