SEATTLE — Throngs of demonstrators rallied downtown today in protest of the first visit to the U.S. by a Vietnamese prime minister since the war's end 30 years ago.

Prime Minister Phan Van Khai's Northwest stop kicked off his weeklong U.S. tour to promote trade and strengthen diplomatic ties.

Protesters lined up early on a sidewalk across the street from the Fairmont Olympic Hotel, where Khai planned a press conference Sunday afternoon. The crowd was estimated at 150, according to Seattle police Sunday morning, but organizers said the number had doubled within hours as people arrived from California, Oregon and British Columbia, Canada.

No more than a dozen police officers were seen standing in small groups around the hotel.

Demonstrators shouted "Down with Communists" and held signs that read "Khai is another Saddam Hussein." Crowds waved the former gold and crimson flag of Vietnam as people called for an end to political and religious persecution in that country.

Sai Nguyen, an organizer with the Vietnamese American Coalition in Northwest America, criticized the Communist Party's push to open it's economy to foreign investors, saying it would not improve the lives of Vietnamese people.

"Now they're talking about investment from overseas, but the goal is not to help the people. It is only to help the party," he said.

The demonstrations would let Khai know that Vietnamese Americans want him to address human-rights abuses that continue in Vietnam 30 years after the war, said Nhien Le of Kent, a former officer in the South Vietnamese Air Force.

"Compared with all the countries in southeast Asia, we are at the bottom. That's why we fight for the freedom," Le said.

It's important that Americans know that abuses persist in Vietnam, said Minh Vuong of Kent, a representative of the Vietnam Reform Party. He called on Khai to free religious and political prisoners and to end the black-market trade of sex-workers in southeast Asia.

He said Khai would be followed by protests of Vietnamese Americans during his U.S. tour.

"We don't let him have the freedom in the United States and we have to let him know what freedom really is," Vuong said.

Khai, 71, arrived Sunday morning with a stop first at Boeing's plant in Renton, south of Seattle, to oversee the purchase of four 787 Boeing jetliners by Vietnam Airlines. He and his 15-person entourage toured the plant for less than an hour, accompanied by Mark Jenkins, vice president and general manager of Boeing's 737 programs and Raymond Conner, vice president of sales for the Americas.

Khai then headed to Issaquah for a brief visit with a local Vietnamese family before heading to Seattle.

On Monday, he is to visit Microsoft's Redmond campus "to continue reinforcing the collaboration" between the company and Vietnam's government, a company spokeswoman said Friday. Microsoft has an office in Vietnam.

He'll then depart for visits to the New York Stock Exchange, Harvard University and the White House.

In the nation's capital, he'll seek President Bush's help in gaining Vietnam's admittance to the World Trade Organization.

In the 10 years since diplomatic ties were restored, the United States has become Vietnam's top trading partner. U.S. investment in Vietnam has risen 27 percent each year since a bilateral trade agreement took effect in 2001.