Taliban militants have intensified activities amid the visit of Admiral Mike Mullen, chairman of the U.S. Joint Chiefs of Staff, to Afghanistan as over a dozen policemen have been killed over the past 24 hours in the post- Taliban nation.

In the latest wave of violence and apparently coordinated attacks, the militants raided police checkpoints in the restive southern Helmand province and the relatively peaceful northern Baghlan province killing at least 15 police constables late last night and this morning.

Anti-government militants stormed a police checkpoint in Baghlan-e-Markazi district of Baghlan province late Sunday night killing seven police constables, a police officer Ahmad Jan told Xinhua.

He also added that a militant commander Qari Mansoor was killed in the firefight.

In a similar incident the militants killed seven policemen in the militancy-hit Helmand province in south Afghanistan early Monday, spokesman for the provincial administration Daud Ahmadi said.

Furthermore, Taliban insurgents wounded one police constable in an engagement with police in the northeast Takhar province at 11: 00 a.m. local time, according to provincial police chief Ziadin Mahmoudi.

Mahmoudi also stressed that one Taliban fighter was killed and three others were made captive in the firefight that lasted for a while.

The top U.S. commander Admiral Mike Mullen who paid a surprise visit to Afghanistan Monday morning said that Washington would continue to support Afghan security forces.

"We must quickly reverse the momentum of insurgents and build up the capacity of Afghan army and police to provide security of their own county," he told a press conference after meeting Afghan Defense Minister General Abdul Rahim Wardak.

He also emphasized that the U.S. and NATO-led troops would continue to target and eliminate the Taliban and al-Qaida leaders.

Since announcing sending in additional 30,000 troops to Afghanistan by President Barack Obama early this month, Admiral Mullen is the fourth western dignitary touring the militancy- plagued Afghanistan.

Previously, U.S. Secretary of Defense Robert Gates, German Defense Minister Karl-Theodor zu Guttenberg, British Prime Minister Gordon Brown have visited Afghanistan to show support to the Afghan administration in war on terror and militants.

"Our troops are here only as long as it takes to help you defeat your enemies, we will fight by your side until Afghan forces are large enough and strong enough to secure the nation on their own as they have already done in Kabul," Gates told journalists last Tuesday in President Hamid karzai's Palace.

"Our relationship with Afghanistan is long term commitment," he said at a joint press conference with President Karzai.

Military commanders and experts are of the view that 2010 would be critical and the insurgents' activities would go up in spring.

Afghan Defense Ministry spokesman General Zahir Azimi predicted in talks with media on Monday that the insurgents would intensify attacks when the weather gets warm.

Meantime, an operation launched some two weeks ago in parts of Helmand province, according to officials, have left over 50 militants dead.

Taliban elusive leader Mullah Mohammad Omar who has escaped the U.S. manhunt over the past eight years, vowed to continue Jihad or holy war against the U.S.-led mission in Afghanistan in a message to Obama's troop surge strategy.