It was in the form of a sit-in, with protesters parking their cars on the street leading to the US embassy in capital Manama on Friday.
The protesters demanded the unconditional release of al-Khawaja and the reopening of the Bahrain Centre for Human Rights, of which al-Khawaja is a memeber.
In a statement, the committee said security officers tried to prevent them from assembling. The number of the cars exceeded 200 and resulted in a traffic jam.
The public prosecuter has accused al-Khawaja of "provoking hatred against the regime and fabricating agitating rumors."
This charge was made after his talk at the Human Rights Centre about financial and administrative corruption leading to increased poverty in the country.
Al-Khawaja,43, returned to Bahrain in 2001 with his family after a 22-year self-imposed exile in Europe. He was arrested a day after his speech at the centre in which he called for the resignation of the prime minister.
Bahrain's king, Shaikh Hamad bin Isa al-Khalifa, has taken steps since assuming the throne in 1999 to move the country from an absolute monarchy to a constitutional one. He has pardoned more than 1000 political prisoners and allowed exiles to return.
In 2002, Bahrain held its first parliamentary elections since 1971.
However, critics charge his reforms do not go far enough towards ensuring freedom of expression and democracy.