Afghan and NATO forces battling insurgents said Tuesday that 35 people have died in escalating violence as the Taliban try to regain territory lost during the winter months to the U.S.-led alliance.

There has been fierce fighting around Afghanistan, but most has been focused in the southwestern Helmand province and other parts of the southern Taliban heartland. Violence has increased since the insurgents launched an offensive last April.

The office of Helmand Gov. Gulab Mangal said that two separate clashes on Monday left a total of 22 insurgents and two police officers dead. The governor's office also said two young boys were killed as they stepped on a roadside bomb in Helmand.

The provincial capital, Lashkar Gah, was one of seven areas where the coalition last week handed over responsibility forsecurity to Afghan forces. The handover was part of a transition plan that eventually will give the Afghan government control of security around the country by the end of 2014, when foreign combat troops are to leave Afghanistan.

Monday's clashes occurred in central and northern Helmand, the statement from the governor's office said.

In one of the clashes, eight insurgents were killed near the town of Nadiali — located near the provincial capital. Another 14 were killed and eight wounded when they attacked a police checkpoint in the Musa Qala district. The two police officers were killed in that attack, the statement said.

NATO announced separately that nine insurgents were killed Monday in three separate incidents elsewhere in Afghanistan, including five during a raid to capture a local Taliban leader in eastern Laghman province.

Meanwhile, Afghanistan President Hamid Karzai has told his country's soldiers and police that they face a difficult year ahead as they take on more security responsibilities.

But he wants them to push ahead so that Afghanistan can eventually defend itself. He said Afghans should be "thankful for the help" from NATO and the international community but it's shameful that it was needed.

Karzai made his comments Tuesday during an assembly of Afghan officers in the yard of the presidential palace in Kabul. He urged the assembled officers to work hard and sacrifice to ensure success.