MIRANSHAH, Pakistan, Aug 4 (Reuters) - At least 22 people were killed on Saturday in spiralling violence in northwestern Pakistan as international concern grew over the deteriorating security situation and al Qaeda threat along the Afghan border.

Soldiers repulsed an attack by pro-Taliban militants in North Waziristan, and a suicide car bomber struck in another tribal area bordering Afghanistan.

North Waziristan is regarded as a hotbed of al Qaeda and Taliban support, and the United States is expecting the Pakistani military to strike at select targets after militants abandoned a peace pact in the semi-autonomous tribal region last month.

While there has been no offensive yet, the army has reinforced check posts and stepped up patrols, provoking a series of attacks in recent weeks that have added to mounting concern over the country's a deteriorating security situation.

How to make Pakistan do more to eradicate al Qaeda hideouts has become a hot topic in the U.S. election campaign, with Democratic hopeful Barack Obama talking of American forces conducting operations or strikes inside Pakistani territory.

During a telephone call to President Pervez Musharraf, U.S. President George W. Bush said this kind of talk was "unsavoury", and assured the Pakistani leader Washington respected its ally's sovereignty, the Pakistani Foreign Ministry said on Friday.

On the ground, in a pre-dawn attack on Saturday, militants bombarded a check post in the Dosali area, some 40 km (25 miles) south of Miranshah, North Waziristan's main town.

Troops repulsed the guerrillas when they launched a direct assault on the post.

"Militants fired about 50 rockets on a check post complex at around 0300 hours (2200 GMT Friday) and then they carried out a physical attack on the check post," military spokesman Major-General Waheed Arshad said.

"Four security forces were killed and four wounded, while 10 militants were also killed in the attack."

Arshad said the militants had fled after about two hours carrying four to five bodies with them.

In the neighbouring Kurram tribal region, a suicide car bomber rammed another car on a road through a bazaar in the main town of Parachinar, paramilitary officer Mohammad Kafeer said.

"The death toll has reached eight and there are another 37 people being treated for blast wounds," Dr. Hanif Jan, medical superintendent at Agency Headquarters Hospital in Parachinar, told Reuters. Two wounded were in a critical condition.

Violence has intensified in Pakistan since last month's military assault on Islamabad's Red Mosque to crush a militant Islamist movement.

Some 102 people were killed during the siege and assault on the mosque, and more than 200 have since died in bombings and clashes across the country.

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