Afghan bombings kill US Marines

Four US Marines have been killed in Afghanistan, the US military has said.

The troops died in two separate improvised roadside bomb attacks on Saturday, US forces spokeswoman Christina Sidenstricker said.

The latest deaths mean US forces are suffering their highest casualty rates since operations began in 2001.

UK forces are also suffering heavy losses, with 15 killed in 10 days. US President Barack Obama has praised the ongoing military effort.

He said Taliban rebels were being pushed back as Afghanistan prepared for elections.

US Marines and British troops recently launched a major new offensives against the Taliban in southern regions of Afghanistan.

Casualty figures have spiked in the past few weeks as insurgents have mounted new attacks and military action has increased in intensity.

More than 100 US soldiers have been killed since the start of this year.

Reuters news agency reported that another Nato soldier died on Friday from wounds received in June.

In the UK, Prime Minister Gordon Brown has been forced to defend the country's involvement in the Afghan mission as the numbers of British casualties rises.

Speaking in a Sky TV interview, Mr Obama said the battle in Afghanistan is a "serious fight" but one essential for the future stability of the country.

He said new strategies for building bridges with Afghan society would be considered once the country had held its presidential election.

The country is due to hold a presidential vote in August.