Washington state's attorney general is suing President Donald Trump over an executive order that suspended immigration from seven countries with Muslim-majority populations.

Attorney General Bob Ferguson announced his lawsuit on Monday, becoming the first state attorney general to announce a legal action against the Trump administration over one of its policies.

President Trump signed an executive order on Friday that suspends all immigration for citizens of the seven countries for 90 days.

Mr Ferguson was one of 16 state attorneys general who released a statement on Sunday calling Mr Trump's immigration action "un-American and unlawful".

President Trump's order sparked large protests around the country over the weekend.

Mr Trump has repeatedly said that the move is aimed at protecting the nation against extremists looking to attack Americans and American interests.

The president has repeatedly said that the move is aimed at protecting the nation against extremists looking to attack Americans and American interests.

Mr Ferguson said the lawsuit against Trump and high-ranking Trump administration officials would be filed later on Monday in federal court in Seattle.

He said it would seek to have key provisions of the executive order declared unconstitutional.

The lawsuit also seeks a temporary restraining order against enforcement of the executive order.

"We've had folks in our office working all weekend on a legal action," said Mr Ferguson, who was joined at a news conference by Washington Gov Jay Inslee.

"This is un-American, it is wrong, and it will not stand," Gov Inslee said.

"The clear intent of this executive order is to discriminate against one faith amongst all God's children."

Mr Ferguson said he has been in contact with other attorneys general, but that at this point Washington state was acting on its own regarding the legal action.

The Port of Seattle said over the weekend that people who were detained at Seattle-Tacoma International Airport as a result of President Trump's order have been released.

US Rep Pramila Jayapal said on Sunday that two individuals were released.

One is a citizen of Sudan and the other a citizen of Yemen, both countries named in President Trump's order.

AP