DUBAI, United Arab Emirates - Two Saudi women detained for nearly a month in defiance of a ban on women driving were referred Thursday to a court established to try terrorism cases, several people close to the defendants said.

The cases of the two, Loujain al-Hathloul and Maysa al-Amoudi, were sent to the antiterrorism court in connection to opinions they expressed in tweets and in social media, four people close to the women told the Associated Press.

They did not elaborate on the specific charges or what the opinions were. Both women have spoken out online against the driving ban. Activists say they fear the case is intended to send a warning to others pushing for greater rights. The four people spoke on condition of anonymity because of fear of government reprisals.

The Specialized Criminal Court, to which their cases were referred, was established in the capital Riyadh to try terrorism cases but has also tried and handed long prison sentences to a number of human rights workers, peaceful dissidents, activists and critics of the government. For example, this year it sentenced a revered Shiite cleric Sheikh Nimr al-Nimr, a vocal critic of the government, to death for sedition and sentenced a prominent human rights lawyer, Waleed Abul-Khair, to 15 years in prison on charges of inciting public opinion.

Human Rights Watch recently warned that "Saudi authorities are ramping up their crackdown on people who peacefully criticize the government on the Internet." It said that judges and prosecutors are using "vague provisions of a 2007 anti-cybercrime law to charge and try Saudi citizens for peaceful tweets and social media comments."

This was the first time women drivers have been referred to the court, activists said.

The detention of Hathloul, 25, and Amoudi, 33 - both arrested Dec. 1 - has been the longest yet for any women who defied the driving ban. They were supporters of a grassroots campaign launched last year to oppose the ban, and had a combined 355,000 followers on Twitter at the time of their arrest.

Though no formal law bans women from driving in Saudi Arabia, ultraconservative Saudi clerics have issued religious edicts forbidding women from taking the wheel, and authorities do not issue them driver's licenses. No such ban exists anywhere else in the world, even in other conservative Persian Gulf countries.

The four people close to the women said their lawyers appealed the judge's decision to transfer their cases. An appeals court in Dammam, the capital of Eastern Province, is expected to decide on the referral in the coming days, they said.