BISMARCK, N.D. — Abortion-rights advocates have filed a lawsuit in federal court challenging two new North Dakota laws that impose the nation's toughest abortion restrictions.

The New York-based Center for Reproductive Rights is representing the Red River Women's Clinic in Fargo in the lawsuit filed Tuesday. It seeks to block a measure that would ban abortions as early as six weeks into a pregnancy, when a fetal heartbeat can first be detected. The lawsuit also is challenging another new law that would prohibit women from having an abortion because a fetus has a genetic defect, such as Down syndrome.

Abortion-rights activists say the laws are unconstitutional.

North Dakota lawmakers already have set aside $400,000 for the legal fight promised by abortion-rights activists.