Roadside bombs killed three NATO troops and a gunman shot dead a prominent local official in southern Afghanistan, where thousands of Afghan and international troops are bracing for an expected spring resurgence of Taliban attacks, officials said Sunday.

NATO said one troop died in a blast Sunday and two others were killed in an explosion on Saturday.

Earlier, the alliance said that a fourth died Saturday when a coalition helicopter crashed in Alasay district of Kapisa province in the east.

It did not provide any further details, or nationalities of those killed.

The deaths brought to 134 the number of NATO troops killed in Afghanistan this year.

Afghanistan's spring fighting season is expected to be in full force by the end of this month or early May. Before last winter set in, tens of thousands of U.S. and NATO reinforcements routed the Taliban from their strongholds, captured leading figures and destroyed weapons caches, especially in the east and south.

The militants, known for their resiliency, have responded with high-profile attacks across the nation.

A gunman assassinated Abdul Zahir, deputy of the Helmand provincial peace council and former top civilian chief in Marjahdistrict, late Saturday in the provincial capital of Lashkar Gah, the Ministry of Interior said Sunday.

Zahir also was a member of the local improvement council for the area and a leading member of the Alizai tribe.

The Taliban claimed responsibility for the killing in a telephone call to The Associated Press.

Afghan President Hamid Karzai said he was saddened by the death of Zahir, a man he described as "a brave son of this homeland."

Zahir's appointment as Marjah district chief early last year became controversial when court records and news reports in Germany showed that Zahir served part of a more than four-year prison sentence for attempted manslaughter for stabbing his son in 1998.

Insurgent group leaders killed

A U.S. official confirmed that Zahir had a criminal record in Germany, but Zahir denied ever spending time in a German jail.

His criminal record was at issue because at the time he was the man tasked with convincing residents of Marjah that the Afghan central government could better provide for them than the Taliban.

Afghan and coalition forces launched a major offensive in Marjah in February 2010 to rout insurgents from their strongholds in Helmand.

Afterward, Zahir was appointed the face of a new local government, a key test of NATO's counterinsurgency strategy.

NATO also confirmed Sunday that Afghan and coalition forces have killed three leaders of the Haqqani network, an insurgent group with close ties to al-Qaeda that operates primarily in Paktika, Paktia and Khost provinces. So far this year, more than 15 Haqqani leaders and more than 130 other insurgents affiliated with the network have been captured or killed.

More than 90 of those captured were taken in Khost province, where the three died on Friday.

Among those killed was Salih Khan, a senior Haqqani leader in Nadir Shah Kot district. According to the coalition, he trained bomb makers, orchestrated car bombings and handled logistics and communications for insurgents in the area.

During the past week, Khan led 20 fighters in two attacks on coalition forward operating bases, the coalition said.