A roadside bomb and a rocket-propelled grenade in southern Afghanistan killed two British soldiers, while gunmen in the east abducted 16 mine-clearing personnel working for the United Nations, officials said Sunday.

The attacks that killed the British troops in Helmand province's Gereshk district came as thousands of U.S. Marines pour into the Taliban's southern heartland, in the biggest U.S. military offensive operation in Afghanistan since the toppling of the militants in 2001.

Click for photos from the Marine offensive.

It wasn't clear if the British casualties were involved in the Marine operation taking place in the same province.

Britain's Ministry of Defense said both attacks took place near Gereshk in Helmand province on Saturday. Earlier the NATO-led force said the two had died in a single incident. It was not immediately clear what caused the discrepancy in the accounts.

Taliban militants frequently use roadside bombs in their fight against Afghan and foreign forces in the country.

Responding to the deteriorating security situation, President Barack Obama's administration has ordered 21,000 additional troops to Afghanistan and expects the total number of U.S. forces there to reach 68,000 by year's end. That is double the number of troops in Afghanistan in 2008 but still half as many as are now in Iraq.

In the country's east, meanwhile, gunmen kidnapped the 16 Afghan deminers as they traveled between Paktia and Khost provinces on Saturday, said Paktia's police chief Azizullah Wardak.

While insurgents operate in the area, Wardak could not say who was responsible for the kidnapping. Similar incidents have happened twice before in Paktia but were resolved successfully, he said.

Wardak criticized the demining team — part of the U.N.'s effort to rid the country of decades of planted land mines — for going into the area without informing the police.

Afghanistan is one of the most heavily mined countries in the world, and the increase in violence amid a thriving Taliban insurgency has slowed clearance work. Some 50 people are killed and maimed by mines every month.

Two-thirds of the country's mines have been cleared over the past two decades, with the rest expected to be removed by 2013. But experts fear Afghanistan can no longer meet that goal because of increased fighting and a drop in international funding.

Trained deminers have increasingly been targeted and killed by militants. Last year, insurgents shot and killed six mine clearers in one day and two the next, according to the United Nations Mine Action Center.

Militants often use the raw materials from the mines to make roadside bombs and other improvised explosive devices.

Mines in Afghanistan are a legacy of decades of Soviet occupation and subsequent civil war. Tens of thousands of mines and unexploded ordinance still pepper the rugged country.