LINK By Jon Hemming 2 hours, 41 minutes ago KABUL (Reuters) - More foreign fighters are joining the ranks of Taliban insurgents in Afghanistan as militants increasingly cross the border from Pakistan to attack Afghan and Western troops, the Afghan Defense Ministry said on Wednesday. Afghanistan has kept up a barrage of criticism against neighbor Pakistan in the last three months, accusing Pakistani agents of being behind a string of high-profile attacks and allowing militants sanctuary along the long and porous border. "The presence of foreign fighters is increasing, and increasingly the operations of the terrorists are led by foreigners," Defense Ministry spokesman General Mohammad Zaher Azimi told a news conference. Afghan, NATO and U.S.-led coalition forces are struggling to contain a sharp surge in violence as the traditional summer fighting season gets into full swing. Already more U.S. troops were killed in Afghanistan in May and June than in Iraq, where there are some four times more American soldiers. July, usually the peak month for fighting, could well be the worse month yet for violence since U.S.-led and Afghan forces toppled the Taliban in 2001. Security analysts predict the number of violent incidents could top 1,000 for the first time. As well as more violence, Afghan and foreign troops are reporting a greater sophistication in Taliban tactics such as multiple roadside bombs and complex ambushes, factors indicating more training and possibly the presence of foreigners. TALIBAN LEADERS TARGETED Admiral Mike Mullen, chairman of the U.S. joint chiefs of staff, said this month there were indications that al Qaeda was switching its focus from Iraq back to Afghanistan. Violence has increased by 40 percent in the last two months compared to last year, NATO says, partly due to the improved weather, but also due to ceasefires between troops and militants in Pakistan's border tribal belt. Afghanistan believes foreign funding for the Taliban is channeled through Pakistan's Inter-Service Intelligence (ISI) agency, Azimi said. Money for the insurgency comes through donors in Gulf countries and a tax on Afghanistan's booming drug trade, security analysts say. Afghan security forces have launched a series of operations along the main highway that loops around the south of Afghanistan, killing around 100 militants in the last two weeks, Azimi said. Meanwhile, Afghan and international troops have killed 20 senior militant leaders, including one from al Qaeda, in the last month and captured another seven, he said. Western troops in Afghanistan have concentrated on targeting the Taliban leadership in an effort to degrade the insurgent fighting ability.