Kabul, Afghanistan (CNN) -- A top Haqqani network leader suspected of providing support for Tuesday's deadly attack at a Kabul hotel was killed in an airstrike in southeast Afghanistan, the International Security Assistance Force said Thursday.
Ismail Jan, who is the deputy to the senior Haqqani commander, and several fighters were killed in a precision airstrike Wednesday in Paktiya province.
Jan was an insurgent leader in the Khost-Gardez Pass area, along the Afghanistan-Pakistan border, the international coalition said.
Afghan government officials blamed the al Qaeda-linked militant group for the siege on the Kabul Hotel Inter-Continental that left 12 victims and all nine attackers dead.
The level of violence in the country was signficantly higher in the past three months than it was in the same period last year, the United Nations said Thursday.
There were 17 suicide attacks in April 2011, more than in any single month last year, the world body said.
Kandahar suffered the most, with most of the incidents in the quarter taking place in the city or nearby.
Nearly 3,000 Afghan civilians were killed or wounded, 80% of them as a result of "anti-government elements."
The attackers who struck the Hotel Inter-Contintental were with the Haqqani network, said the Afghan interior ministry.
The group of terrorists loyal to the warlord Siraq Haqqani is based in Pakistan.
They entered the hotel late Tuesday night by avoiding the main entrance and attacking a smaller one on the other side of the hotel that was guarded by two Afghan police, said Falak Merzahi, a spokesman for the interior ministry.
The attackers killed the two officers and stormed the hotel, Merzahi said.
Six of the attackers ended up detonating their explosives; three were shot and killed on the roof of the hotel, Afghan officials said.
Although a NATO helicopter carrying International Security Assistance Force snipers flew to the scene and fired at the attackers, Merzahi said it was Afghan army soldiers who ultimately killed the three gunmen on the roof.
ISAF said its forces stopped firing on the roof when Afghan soldiers arrived.
The 12 others killed are two police officers, nine Afghans and one foreigner, Merzahi said.
Afghan President Hamid Karzai said the attack will not interrupt the planned handover of power from international forces to Afghan troops.
President Barack Obama has said U.S. troops will start withdrawing from Afghanistan in July, and that a military handover should be completed in 2014.