Hundreds of heavily armed Taliban besieged a Pakistani checkpost on the Afghan border for a second day Thursday, killing 23 police and five civilians in the deadliest fighting for months. A senior police official told AFP that 500 militants, including Afghan Taliban from across the border and Pakistani Taliban, took part in the attack which began before dawn on Wednesday and continued more than 24 hours later. Officials said the militants targeted the Shaltalu checkpoint, surrounded by mountains and forest in the northwestern district of Upper Dir, about six kilometres (four miles) from the border with Afghanistan\'s Kunar province. The Pakistani military sent reinforcements to the police checkpost, deploying helicopter gunships in a bid to quell the attack along the porous border, where Taliban and Al-Qaeda-linked militants are dug in. \"We have regained control of most of the area but fighting is still going on in some parts near the checkpost, which was attacked by around 500 Pakistani and Afghan Taliban,\" senior police official Qazi Jamil ur-Rehman told AFP. He said 28 people were killed in the attack, including 23 policemen and five civilians, among them two women, who died when mortar bombs fired by militants targeting the post landed in nearby houses. Rehman said more than 20 police personnel were wounded, but he had no information on casualties among the Taliban. \"Frontier Corps (paramilitary) troops, army helicopters and artillery and police personnel are taking part in the operation,\" said Rehman. Taliban and other Islamist militants have carved out strongholds on both sides of the porous Afghanistan-Pakistan border, a region that the United States has called one of the most dangerous regions on Earth. Upper Dir is part of Pakistan\'s northwestern Khyber Pakhtunkhwa province and borders the region where the military waged a major offensive to put down a local Taliban insurgency in Lower Dir, Buner and Swat in 2009. Thousands of Pakistanis have died in bomb attacks over the last four years and thousands more soldiers have been killed fighting homegrown militants. But since US Navy SEALs found and killed Al-Qaeda founder Osama bin Laden in the town of Abbottabad on May 2, Washington has increased pressure on Pakistan to take more decisive steps. On Wednesday, the commander in Khyber Pakhtunkhwa played down \"media hype\" over the prospect of an imminent military offensive in North Waziristan, considered the premier militant fortress on the Afghan border. Local newspaper The News reported this week that Pakistan had decided to launch a \"careful and meticulous\" military offensive in North Waziristan after US Secretary of State Hillary Clinton\'s recent visit to Islamabad. But Lieutenant General Asif Yasin Malik, the corps commander supervising all military operations in the northwestern province of Khyber Pakhtunkhwa, told reporters: \"We will undertake operation in North Waziristan when we want to.\" The remote, mountainous region has attracted major interest in the United States as a fiefdom of the Haqqani network, one of its most potent enemies across the border in Afghanistan and thought to have a core of 4,000 fighters. The Al-Qaeda-linked group attacks only across the border in Afghanistan, and is said to have long-standing ties to Pakistan\'s intelligence services. A private Washington think tank is now warning that the United States should delay much of a multibillion-dollar package to Pakistan pending economic reforms as the aid has led to official inaction and public resentment. A report by the Center for Global Development said that US assistance to Pakistan had become \"muddled\" with a lack of clear goals and leadership and pressure \"to do too much, too quickly.\" US lawmakers are questioning aid to Pakistan -- which has totalled $20 billion since the September 11, 2001 attacks -- since the bin Laden debacle.