Amateur video footage posted on the internet shows Syrian forces on the streets of Deraa rounding up hundreds of pro-democracy sympathisers Reuters

Scores of Syria's most prominent intellectuals and activists have gone into hiding as government forces try to crush dissent by carrying out raids and arrests in towns and cities across the country.

Influential political figures including the lawyer Haitham al-Maleh and doctor Walid al-Bunni, whose prominence has until now protected them, have joined younger activists in fleeing their homes.

Security forces rounded up more than 70 people in Zabadani and Idleb on Monday and dozens more in Kafer Nabul, 200 miles north of Damascus, activists said.

At least three women were arrested at a protest in Hamra street, in the centre of the capital as all-female groups increasingly take to the streets to protest against the violence and arrests, the brunt of which has been borne by men. One of those held was named as Dana al-Jawabra.

The arrests continued in a wave in Deraa on Sunday, with residents saying security forces backed by soldiers marched from house to house methodically selecting people and carrying them away in buses and trucks. Kurdish sources also said seven people had been arrested in the north-eastern towns of Qamischli and Amouda, where large protests have been held. The state news agency, Sana, gave a different version of arrests in Deraa, saying army units had arrested 499 members of "terrorist groups" and killed 10 of their members.

The authorities also set a deadline of 15 days for people who had committed "unlawful acts" to give themselves up.

Seeking to increase pressure, security forces are increasingly targeting the families of known activists. Human rights monitors said the 22-year-old nephew of the political activist Ayman al-Aswad, Osama, had been arrested in Deraa.

Razan Zeitouneh, a lawyer who has been in hiding since the end of March, said her husband had also gone underground after security forces raided their house and arrested her 20-year-old brother-in-law over the weekend.

"It is not easy but we have no choice if we want to work," said Zeitouneh, adding that she believed she would be found and arrested at some point.

Foreigners appear no longer immune from arrest as al-Jazeera announced it had not heard from journalist Dorothy Parvaz since she landed in Damascus last Friday.

Human rights organisations estimate the Syrian authorities have detained more than 7,000 people since protests calling for the regime to go began in mid-March. About 600 have also been killed.

Those emerged report tales of torture and the confiscation of personal belongings including money. One man recently released told the Guardian that he had been badly beaten and prodded with electric tasers.

Despite the arrests and violent clampdown, protests posing the biggest challenge to over 40 years of Assad family rule have continued, with violence leaving a trail of devastation across parts of the country.

Rastan, a town close to Homs where 13 were killed on Friday, is described by witnesses as a "war zone" littered with tanks, sandbagged checkpoints and burned-out cars.

On Monday a humanitarian aid convoy was due to depart from the Jordanian border for the besieged southern city of Deraa from where accounts of devastation continue to emerge.

Katherine Marsh is a pseudonym for a journalist living in Damascus