Afghan soldiers patrol last month in Nangahar province near where U.S.-led forces dropped a GBU-43 bomb on caves used by the Islamic State. (Ghulamullah Habibi/European Pressphoto Agency)

Seeking to capitalize on the death of a top Islamic State commander, Afghan forces have surged through districts in eastern Afghanistan long held by the radical Islamist group as warplanes have pounded militant hideouts in the past week, officials said Monday.

The offensive in Nangahar province is targeting Islamic State fighters at a time when their numbers are down and their leadership is in disarray after a U.S.-Afghan commando raid in late April killed the group’s senior regional leader, Abdul Hasib.

It also underscores the intensifying focus on Nangahar, where on April 13 the U.S. military dropped its largest non-nuclear bomb on a complex of caves and tunnels used by the Islamic State, reportedly killing 36 militants. Nangahar, on the border with Pakistan, is a main route for militant fighters and supplies.

As Afghan forces have advanced into some villages for the first time in months, Islamic State fighters are pushing back amid heavy fighting in several adjacent districts, officials said.

Afghan officials said at least 34 militants had been killed by Afghan airstrikes since Sunday but gave no figures on Afghan casualties. The role of U.S.-led coalition forces in the latest phase of the offensive was not immediately clear. 

The killing of Hasib in an April 27 night raid, announced Sunday by the Pentagon and Afghan President Ashraf Ghani, was carried out by a team of 50 U.S. and 40 Afghan special-operations forces. They assaulted a cluster of village buildings where Hasib and other Islamic State militants were staying, killing all of them and 35 guards.

Officials said the announcement of Hasib’s death was delayed until his remains could be positively identified. 

The killing was the third major blow in recent months to the Islamic State in Khorasan, or ISIS-K, the regional branch of the Sunni extremist group based in the Middle East. The branch’s forces include former Pakistani Taliban, Uzbeks and other foreign fighters.

Two U.S. Army Rangers also died during the April 27 operation, U.S. officials have said. They have been identified as Sgt. Joshua P. Rodgers, 22, of Bloomington, Ill., and Sgt. Cameron H. Thomas, 23, of Kettering, Ohio. Military officials said that their deaths may have been caused by friendly fire and that the incident is under investigation.

That raid came eight months after the previous ISIS-K leader, or emir, Hafiz Saeed Khan, was killed in a U.S. drone strike.

“This successful joint operation is another important step in our relentless campaign to defeat ISIS-K in 2017,” Gen. John Nicholson, commander of U.S. forces in Afghanistan, said in a statement about Hasib’s death. 

Afghan officials described Hasib as a charismatic and ambitious commander who orchestrated several high-profile attacks, including the March 8 stealth assault on Kabul’s military hospital that killed scores of patients and staffers. Hasib, whose age was not known, was a Taliban commander in Logar province who defected to ISIS-K. He was also known as Abdul Hasib Logari. 

“He was responsible for ordering the attack on the 400-bed hospital in Kabul, he kidnapped girls and beheaded elders in front of their families,” the president’s office said Sunday night on Twitter. 

In early March, Afghan and U.S. special forces launched the current counteroffensive against ISIS-K, backed up by drone strikes, killing hundreds of its fighters and clearing numerous villages.

A U.S. military spokesman in Kabul, Navy Capt. William Salvin, estimated that the ISIS-K force has been reduced from more than 2,500 fighters at its peak in 2015 to fewer than 600, mostly confined to several adjacent districts in Nangahar. 

“They are still fighting very hard, but we intend to keep the pressure up until we destroy them,” Salvin said Monday. 

Ataullah Hoghiani, a spokesman for the Nangahar governor, said the Islamic State had lost 40 percent to 60 percent of its fighting strength in the province. The Interior Ministry said government airstrikes had also destroyed a clandestine radio station that ISIS-K used to broadcast religious messages.

The presence of the Islamic State in Afghanistan has complicated the fight against the indigenous Taliban insurgents, stretching Afghan forces thin and introducing extreme anti-Shiite sectarianism in a country with a large Shiite minority. It has lured some Taliban members and created rivalries with others.

Over the past several days, Taliban fighters have overrun a district in the northern province of Kunduz, and local security forces and officials said they were waiting for help and reinforcements. 

A local police official, Azizullah Ayar, said that numerous wounded officers were in need of evacuation and that he had urgently asked for help but none had arrived.

“The government does not seem capable to deal with this issue,” Ayar said in a telephone interview. “We have seen no airplanes, even to frighten the Taliban, let alone bomb them.”

Sayed Salahuddin and Sharif Walid contributed to this report.