A flood of refugees flee southern Lebanon in advance of Israeli attacks, while in northern Israel an onslaught of rockets from Hezbollah guerrillas. The U.S. government hunkers down at the approach of an ominous anniversary and 100 years of running through the streets of Boston, a revolutionary race. From ABC, this is World News Sunday. Here's Carol Simpson. Good evening. With each passing day, the situation along the Israeli-Lebanese border grows more unstable and more dangerous. Israel continues its massive air attack on southern Lebanon, while Hezbollah responds with a torrent of Katyusha rockets aimed at northern Israel. And late today, a threat from Hezbollah aimed at the United States and Israel. An unnerving display on Hezbollah-run television showed what it claims are potential suicide bombers, 70 volunteers with explosive devices strapped to their bodies. In the midst of all this, civilians on both sides are being forced to run for cover. Here's ABC's Bill Rettaker. The exodus from southern Lebanon accelerated today. Warned by Israel to leave, 200,000 residents fled the coastal city of Tyre and headed north. Israeli warplanes expanded their zone of influence 20 miles into southern Lebanon. Military officials say they destroyed two Hezbollah radio transmitters and numerous houses used by the guerrillas to launch rockets. Once again, the Air Force showed off its laser-guided missile technology, claiming it demonstrated they were attacking specific targets, like this vehicle parked at the side of a road and this power transformer. The Israelis said they bombed the transformer in retaliation for a Hezbollah attack on a power grid in northern Israel. Israeli long-range artillery again shelled Lebanese villages along the border, but it did not stop Hezbollah from counterattacking. In fact, northern Israel suffered its biggest rocket attack in years. At least 45 rockets fell on settlements in 11 hours, though only a few people were slightly injured. After students had been evacuated from the school, a Katyusha rocket slammed through its roof. Tonight, an underground bomb shelter took a direct hit. No one was hurt, but nerves were badly shaken. Israel's foreign minister insisted that as long as the rocket attacks continued, there would be no hope for a ceasefire. The Lebanese prime minister refused, saying it would be impossible to disarm Hezbollah without risking a civil war. He urged Israel to withdraw and promised to put the Lebanese army in charge if he could get help from the United Nations and France. That offer was rejected. The military campaign continues on day four of Israel's assault against Hezbollah. Bill Redeker, ABC News, Tel Aviv. Late today, the State Department issued a statement accusing Hezbollah of starting this latest round of violence and urged the group to stop the rocket attacks. The large-scale evacuation of American and other foreigners in Liberia has ended for now. What they leave behind is complete chaos, with gangs of young gunmen swarming over the streets of Monrovia. It has been a week since the peace between the Liberian government and rebel forces broke down. ABC's Sheila McVicker arrived today in the Liberian capital. Just outside the U.S. Embassy in Monrovia, some of the scenes of chaos that have led so many to flee the country. Armed militiamen, including teenagers, roam the streets. There is no law or order. Looters are taking everything they can get. International aid agency vehicles, UN computers, air conditioners, all the trappings that made Monrovia function as an African capital are disappearing on the back of pickup trucks. More than 10,000 people, all Liberians, have sought shelter at a U.S. residential compound. Using U.N. trucks, U.S. Embassy staff and Red Cross workers have been able to deliver some food, but conditions there are not good. Many of the refugees were forced to gunpoint to flee their homes, and they have nothing left. They took our clothes, everything, everything, our bags, our guns, everything. Most foreign nationals, including U.S. citizens who want to leave Liberia, have already been airlifted to safety. U.S. Embassy staff estimate there may be only 70 Americans still in the country who want to get out. The U.S. Ambassador says, in spite of the chaos, his Embassy will remain open. We have no plans to pull out of here. This Embassy will stay here, as far as I know, and we intend to stay and be active in the peace process. But tomorrow, all non-essential Embassy staff will be flown out, leaving behind fewer than 20 protected by U.S. soldiers in the midst of a tenuous ceasefire. Sheila Mickvicker, ABC News, Monrovia. Around the nation, there are security concerns as an ominous date, April 19th, approaches. That story when we come back. Also tonight, a look at what three world capitals expect to gain from a presidential trip. And the Boston Marathon, 100 years old and still running. This is World News Sunday, brought to you by Kellogg's. So I just got married, and my husband says, try Crispix. Crispix doesn't get soggy in milk. I love the guy, but nobody's perfect. Okay, it starts off crispy. Now, this spoonful is still crispy, but it's gonna turn soggy. So he makes a little mistake. Kellogg's Crispix cereal, delicious corn and rice that stays crispy to the end. Last bite, it's gonna be soggy. Hey, it's still crispy. He is perfect, so far. Chances are it will outlast your car and your furnace and your roof. There's no telling what your moan, boss, it might outlast. Moan, buy it for looks, buy it for life. Are you taking chances without a calcium supplement? It could take 20 years to find out. By then it may be too late. Which one should you take? Oskal. Oskal's tested and proven effective in clinical studies, and doctor recommended for pennies more a day. Don't take chances, take Oskal. A tragic accident in Montana has claimed the first life in the three week old standoff between federal agents and the so-called Freeman. Special agent Kevin Kramer, 34 years old, was killed today when his car skidded off a dirt road near the Freeman compound. Kramer arrived just yesterday from the FBI's SWAT headquarters in Omaha. Federal agents across the country are on alert this week as a troubling date draws near. A day of special significance among those groups resisting federal authority. Here's ABC's Juju Chang.