A strong 6.5 magnitude earthquake struck the territories of southern Guatemala and El Salvador on Friday, US seismologists said, with local officials grading the tremor slightly lower. The US Geological Survey said the quake struck just six kilometers from Pajapita, Guatemala at a depth 67.7 kilometers (42 miles) at 0013 GMT. The Environmental Observatory in San Salvador said the quake measured 6.3 on the Richter scale and was centered on the coast of Guatemala and Mexico.