Pakistan summoned the U.S. ambassador on Wednesday to protest over missile strikes by pilotless U.S. aircraft on the Pakistani side of its border with Afghanistan, a Pakistani government spokesman said. The protest came two day after missiles fired by a suspected U.S. drone killed up to 20 militants in the lawless South Waziristan border region, Reuters reported. "It was underscored to the ambassador that the government of Pakistan strongly condemns the missile attacks which resulted in the loss of precious lives and property," a Foreign Ministry spokesman said in a statement. "It was emphasised that such attacks were violation of Pakistan's sovereignty and should be stopped immediately."