The first U.S. helicopters flew into Monrovia on Tuesday and began evacuating Americans from the chaotic capital, in the grips of fierce rebel fighting.

Twenty-six Americans, including two children, were on the first flight to arrive safely late Tuesday in neighboring Freetown, Sierra Leone - a two-hour flight from Monrovia - U.S. officials there said.

The fighting that broke out Saturday was the worst in Monrovia since 1993. Liberia, which was founded in 1847 by freed American slaves, has been wracked by civil war since 1990, the fighting broken occasionally by truces that collapse within a matter of weeks.

Late Tuesday, State Department officials said they expect the helicopters to continue shuttling Americans out of Liberia. There are 470 Americans holed up in the West African country.

But, one official said, “We want to avoid use of the word evacuation.” The Pentagon is concerned that an unstable situation could develop if at this point there is a formal announcement of an evacuation, the official said.

Some 15,000 people, many of them foreigners, have crowded into a U.S. Embassy compound since Monday seeking safety from the worst fighting in three years.

State Department spokesman Glyn Davies said U.S. helicopters were ready to take out all of the Americans who wish to leave Monrovia. The helicopters can carry about 25 passengers each.

U.S. Embassy spokesman Dudley Sims had no details on how any further evacuation would be carried out except to say it could take several days.