BOGOTA (Reuters) - Colombia on Thursday said an increasing number of Venezuelans were taking part in attacks by Marxist ELN rebels and in criminal activity, as hundreds of thousands of migrants flee over the border to escape a humanitarian crisis at home. {snip}Villegas said Venezuelans had collaborated with the National Liberation Army (ELN) in attacks in Colombia and been involved in killings and robberies. {snip}Villegas said intelligence agents in Colombia had found that an attack by the ELN in late January, which killed six police officers and injured 40, was planned in Venezuela. He also said that two Venezuelan members...