Activists promoting pacifism and pro-labor causes have sharply questioned a sweeping Federal Bureau Investigation trying to link them to terrorism, the Washington Post reported.

Investigators have issued 23 subpoenas, raided seven homes and sent at least one undercover agent to infliltrate a circle of activists, driven largely by their suspicions that the groups are providing material support to designated terrorist organizations in Colombia and the Palestinian territories. The 23 suboenaed activists have refused to testify before a grand jury, charging that they are being singled out for their political beliefs.

The government appears to be building its case on the contention that even peaceful support for designated terrorist organizations is illegal, a position backed by a 2010 Supreme Court ruling. The advocates are perplexed that their activities, which include trying to help fund a Palestinian women's group and supporting Colombian trade unionists who have been subjected to violence, would be seen as dangerous or illegal. The activists first drew attention for planning an antiwar rally in 2008.

Members of Congress have weighed in to express their concerns. Nine of them have written letters to the administration seeking more information, including Rep. Jan Schakowsky (D-Ill.), a member of the House Intelligence Committee.

Clearly we need to have a bright line where people can exercise their civil rights, their civil liberties, to peacefully protest, Schakowsky told the Post.