The Cairo office of al-Jazeera was ransacked by pro-government "thugs" today, as the Arabic language news channel also said its news website had come under attack by hackers.

Al-Jazeera said its office had been stormed by a "gang of thugs" who burned equipment, on a day of reports of escalating violence against journalists covering the Egyptian uprising.

The Qatar-based broadcaster added that the attacks appeared to be an attempt by "the Egyptian regime or its supporters" to hinder its widely watched coverage of the uprising in Egypt.

It said its website had been hacked earlier today with a banner advertisement replaced with a slogan "Together for the collapse of Egypt", which linked through to a web page with content critical of the network. The banner remained in place for two hours.

"Our website has been under relentless attack since the onset of the uprisings in Egypt [and] we are currently investigating what happened today," said a spokesman for al-Jazeera. "While the deliberate attacks this morning were an attempt to discredit us we will continue our impartial and comprehensive coverage of these unprecedented events."

Last week al-Jazeera's Cairo office was closed by the Egyptian authorities. The broadcaster's reporters have also had their press credentials revoked and nine were detained for periods of time.

In other recent incidents, Swedish TV reporter Bert Sundstrom was in a serious condition in Cairo hospital after being stabbed in the back, according to Associated Press. Dan Nolan, al-Jazeera's UAE correspondent, tweeted today that unfortunately the decision had been taken that it was now too dangerous to remain in Cairo.

"Sadly I'm catching [a] plane out of Cairo today," he said. "Threats to us been about too much. Need to spend some time with family and hope to return soon."

CNN's star reporter Anderson Cooper, who on Wednesday was "roughed up" by thugs on a Cairo street, tweeted today that CNN was now broadcasting from an "undisclosed location" in the city to "stay live as long as we can".

Guardian journalists Peter Beaumont and Jack Shenker were prevented from entering Cairo's Tahrir Square earlier today by both the Egyptian army and armed vigilantes.

Beaumont said the pair were picked up by the army at a checkpoint and made to kneel facing a wall and interrogated. They then had to deal with machete-wielding vigilantes, he added.

However, according to Reuters the Egyptian army has been instructed to assist foreign media and help protect them from groups who have attacked and beaten journalists. Britain and the US have criticised what the US called a "concerted campaign" to intimidate foreign reporters.