Veteran Egyptian labour activist Kamal al-Fayyumi was arrested within hours of the earlier arrests

Egyptian police have arrested an Australian journalist, a US student and their Egyptian translator on suspicion of paying Egyptians to stage protests against the authorities, a security official said.

Austin Mackell, a freelance reporter, Derek Ludovici and Aliya Alwi were detained in the Nile Delta city of Mahalla on Saturday, the same day activists held student strikes to mark the first anniversary of the overthrow of former president Hosni Mubarak.

General Mostafa Baz, police chief of the northern Gharbiya province, told reporters the three were suspected of having co-ordinated over the internet to meet in Mahalla, which has a history of labour strikes, to "incite people to protest".

A security official said people in Mahalla had complained to police that all three were paying people to protest. The authorities have in the past blamed foreigners for plotting unrest.

Alwi said on her Twitter account that they were being charged with inciting protests and vandalism.

"Witnesses have been produced to confirm it," she wrote. "Report against us, filed now. Many witnesses saw us 'offering money to youth to vandalise and cause chaos'."

She tweeted on Saturday evening that they were being handed over to intelligence services. She has not sent any tweets since then, at the time of writing.

Activists and commentators have tweeted developments using the hashtags #freeaustin and #freealiya.

Veteran Egyptian labour activist Kamal al-Fayyumi was also arrested, Baz said, although it was not immediately clear why he had been detained (al-Fayyumi was interviewed by Al Jazeera last April).

The authorities, including the ruling military which took charge after Mubarak's ouster, have accused foreigners of stirring unrest in Egypt which has seen a spate of deadly protests over the past several months.

In June, security forces arrested a US-Israeli citizen they accused of spying and inciting Egyptians to protest. The man, Illan Grapel, was released in October in a prisoners exchange deal.