A leftist guerrilla attack on a hydroelectric dam north of the capital killed 16 soldiers, injured 15 and caused a nationwide power shortage. In San Salvador, a correspondent for the Soviet newspaper Pravda was expelled from the country, and a military judge was fatally shot outside his home. Rebels destroyed five transformers and a central control board during their pre-dawn attack Wednesday at the November 5th Dam, said Col. Carlos Eduardo Melendez of the government's Rio Lempa Hydroelectric Power Authority. The dam, 50 miles north of San Salvador, supplies 22 percent of El Salvador's electricity needs, Melendez said. ``The outage of the system of these five transformers practically leaves the dam out of service for a while. How long we cannot say,'' Melendez told a news conference. He said the attack would worsen an already severe electricity shortage caused by a drought and sabotage by leftist guerrillas, who have fought the U.S.-backed government for the last eight years. The power authority already had planned to start rationing electricity with three-hour daily cuts nationwide beginning Wednesday. The attack forced the authority to increase daily cuts to four hours, Melendez said. Melendez said the guerrillas have mounted about 2,000 attacks on electrical installations causing $51 million in damage since the civil war began in October 1979. The guerrillas' last major attack on the dam was in June 1984. The Soviet journalist, Yuri Stroev, was taken from the Hotel Camino Real on Wednesday by several men who said they were immigration officials, hotel employees said. He was the first Soviet correspondent to visit the country, according to the Foreign Correspondents Association here. The employees, who spoke on condition of anonymity, said the gunmen asked Stroev to pack his luggage and accompany them. He was taken away in a vehicle driven by several plainclothes individuals, they said. An immigration official, who spoke on condition of anonymity, told The Associated Press today that Stroev was deported to Guatemala. He said the journalist had been told he could stay only if he received military accreditation. Stroev had told colleagues earlier that he had applied for accreditation at the Press Committee of the Armed Forces general staff, but officials there had told him they had run out of credentials. Stroev had arrived in San Salvador on Sunday. Also Wednesday, a man jumped from a jeep in a San Salvador neighborhood and shot Jorge Alberto Serrano, a military judge who handles cases related to the civil war. The jeep pulled up outside Serrano's home and the gunman fired four shots into the judge's car, witnesses said, speaking on condition they not be identified for fear of reprisal. The attacker escaped. Serrano, 45, died at the scene. There was no immediate claim of responsibility. Serrano was one of three military judges in charge of national security cases linked to the civil war. Some cases involved people suspected of cooperating with the guerrillas and others involved military officers. In January, Serrano ruled that three men accused in the June 1985 shooting deaths of 13 people, including six Americans, should be freed under an amnesty program implemented in November. President Jose Napoleon Duarte overruled Serrano's decision in April.