Afghan officials say a bomb exploded in a mosque in southern Afghanistan Tuesday, killing at least five people - including the mosque's leader.

Authorities say the explosion took place while the men were worshipping in the mosque in Shah Mansoor village, outside Tirin Kot, the capital of Uruzgan province.    

In other violence, NATO says its troops shot and killed an Afghan civilian near Kabul Tuesday, after the man failed to heed their warnings to stop.

The alliance says the vehicle approached a NATO patrol at high speed north of Puli Alam, the capital of Logar province.  NATO says troops were forced to open fire, after the driver ignored the patrol's signals to stop. 

The issue of civilian casualties has been a source of tension between Afghan President Hamid Karzai's government and the United States. 

The United Nations says more than 2,000 civilians in Afghanistan were killed in militant attacks and NATO military operations last year. 

The U.N. refugee agency, UNHCR, says increased violence caused the number of asylum seekers from Afghanistan to  jump 85 percent last year.

And Polish Prime Minister Donald Tusk announced Tuesday that his country will send 400 more troops to Afghanistan to boost security ahead of elections in August.  Poland currently has 1,600 troops serving in Afghanistan as part of a NATO-led force.

Some information for this report was provided by AP and AFP.