Smoke and flame rise from burning NATO supply oil tankers following an attack by gunmen in the agricultural town of Shikarpur, 400 kilometres (250 miles) north of Karachi on October 13, 2011. Gunmen on October 13 torched four oil tankers in southern Pakistan carrying fuel for NATO troops in Afghanistan, police said. Taliban and Al-Qaeda-linked militants frequently launch attacks on NATO supply vehicles in the northwest and southwest regions of Pakistan, which border landlocked Afghanistan. AFP PHOTO / SHAHID ALI (Photo credit should read SHAHID ALI/AFP/Getty Images) (SHAHID ALI/AFP/GETTY IMAGES)

A U.S. drone strike left four people dead Friday in northwestern Pakistan a day after a similar attack killed the most senior figure struck to date in an escalating campaign against Afghanistan’s Haqqani network.

The four, whose identities were not immediately known, were riding in a car near Miran Shah, the capital of the North Waziristan region and the main base of the Haqqani network. Pakistani officials said the vehicle was struck by two missiles from a U.S. drone, the Associated Press reported.

On Thursday, a CIA drone strike killed Janbaz Zadran, a trusted deputy of network leader Sirajuddin Haqqani and a “close aide” to Haqqani’s brother Badruddin, the group’s top operational commander, a U.S. official said. Zadran “played key roles in resupplying the Haqqani network and insuring the fighters in Afghanistan had access” to the group’s Pakistan-based leadership, the official said.

“It’s probably the most senior death of any Haqqani network member in Pakistan to date, if it’s true,” said Jeffrey Dressler of the Washington-based Institute for the Study of War. “He’s on everybody’s radar.” Dressler and other experts said Zadran was not an active fighter but was in charge of group’s finances and arms shipments.

Before Friday’s drone strike, two militants killed alongside Zadran were buried in the town of Lakki Marwat, AP reported. The funeral of one of the men, Maulana Iftikhar, the head of an Islamic school in Miran Shah, drew 2,000 mourners, including Arab militants and Munawar Khan, a Pakistani lawmaker from the opposition party of former prime minister Nawaz Sharif, the news agency said.

The strikes followed several tense weeks in the U.S.-Pakistan relationship, as the Obama administration publicly alleged direct ties between the Haqqani network and Pakistan’s Inter-Services Intelligence agency.

The United States has said that the Haqqani network is the most significant threat to U.S. and coalition forces in eastern Afghanistan and has warned of increasingly direct action against the militant group’s haven in the Pakistani tribal area of North Waziristan if Pakistan does not move against it.

Pakistani officials said the Thursday attack occurred in Dande Darpa Khel, an area just west of Miran Shah.

The area was the site of several earlier drone strikes, including one in September 2008 that reportedly killed the wife, sister and eight grandchildren of Jalaluddin Haqqani, the founder and patriarch of the group. A drone attack in February 2010 killed Jalaluddin’s youngest son, Mohammad, reportedly a student of religion with no direct involvement in the Afghanistan war.

U.S. officials confirmed that a second drone-fired missile Thursday struck a border town in neighboring South Waziristan. A Pakistani official in the area said the strike killed four militants who were planting explosives.

The strikes came as the U.S. special envoy to Afghanistan and Pakistan, Marc Grossman, arrived in Islamabad, the Pakistani capital, to try to calm rising tensions.

“We tried to think about the future,” Grossman said at a joint news conference with Pakistani Foreign Minister Hina Rabbani Khar. “We also talked about how we can continue in a systematic way to identify the interests we share with Pakistan — and they are many — and then find ways to act on them jointly.”

Pakistan’s relationship with the Haqqanis stretches back to the 1980s, when Islamabad and Washington aided the Afghan group as it fought against the Soviet Union’s military occupation of Afghanistan. Jalaluddin Haqqani became an official in the Taliban government that took over Afghanistan in 1996, and he fled to the Pakistani tribal region, along with al-Qaeda, after the Taliban was overthrown with U.S. assistance in 2001.

Haqqani fighters regrouped and began fighting U.S. and coalition forces across the border in Afghanistan. Pakistan denies U.S. charges that it helps the group but has repeatedly refused to take military action against it. The Haqqani network is separate from, but claims allegiance to, the broader Afghan Taliban movement that is based in Quetta, in southern Pakistan.

In reporting the drone strike early Thursday, a Pakistani intelligence official initially said that the target killed, along with two unnamed Haqqani fighters, was a guard named Jalil Haqqani. The official described him as a “trusted” member of the organization not directly related to the Haqqani family.

But U.S. officials, who were not authorized to discuss intelligence matters, said later that Zadran was the target of the drone strike in North Waziristan and confirmed that he was killed. One official said the apparent confusion may have arisen because Zadran was sometimes known as “Jamil.”

Pakistan’s tribal region, where a stew of militant groups are based, is off-limits to foreigners and dangerous for outsiders, making it difficult to independently verify the details of CIA drone strikes in the area.

Staff writer Karin Brulliard in Islamabad and special correspondent Haq Nawaz Khan in Peshawar, Pakistan, contributed to this report.