Egyptian labour unions have held nationwide strikes for a second day, adding momentum to the pro-democracy demonstrations in Cairo and other cities.
The move comes as demonstrations calling for the immediate resignation of Hosni Mubarak, the Egyptian president, entered their 17th day on Thursday.
Al Jazeera correspondents in Cairo reported that thousands of doctors, medical students and lawyers, the doctors dressed in white coats and the lawyers in black robes, marched in central Cairo and were hailed by pro-democracy protesters as they entered Tahrir [Liberation] Square.
The artists syndicate and public transport workers, including bus drivers, also joined the strikes, our correspondents reported.
"It's certainly increasing the pressure on the government here," Al Jazeera's Steffanie Dekker, reporting from Cairo, said.
"I think it's worth making the distinction that the strikes going on are more of an economic nature, they are not necessarily jumping on the bandwagon of the protesters in Tahrir Square.
"Many of them are not actually calling for the president to step down, but fighting for better wages, for better working conditions."
Pro-democracy supporters across the country have meanwhile called for a ten-million strong demonstration to take place after this week's Friday prayers.
Hoda Hamid, Al Jazeera's correspondent in Cairo, said that the mood in Liberation Square was "one of defiance, and if we judge by what is happening today, then I think ... many more people will heed that call and turn up".
Al Jazeera's Ayman Mohyeldin in Cairo reported that at least five government buildings, including the governor's office and the office for public housing, were set alight in two straight days of riots in the northeastern town of Port Said. The situation in the city had calmed by Thursday evening, he said.
Meanwhile, an immediate investigation has been launched and possible criminal charges could be brought against the senior officer who ordered the firing on protesters during protests on January 28 protests, Moyheldin said.
Click here for more on Al Jazeera's special coverage
The ministry of interior also announced the sacking of the head of security in the New Valley governorate, Moyheldin said.
Also on Thursday, Mahmoud Wagdy, the interior minister, announced that the police were back at work on the streets of the capital.
Meanwhile, Omar Suleiman, the country's vice-president, said on Thursday that his comments to American television station ABC had been taken out of context.
In his interview, Suleiman suggested that Egyptians were "not ready" for democracy. He had also earlier said that if protesters did not enter into dialogue with the Mubarak government, the army may be forced into carrying out a coup.
According to a statement released to a government news agency, Suleiman "emphasised that some sentences in his remarks ... were understood in the wrong way, especially his remarks regarding democratic transition in Egypt".
On Wednesday, Gaber Asfour, the recently appointed culture minister, resigned from Mubarak's cabinet for health reasons, a member of his family told Reuters.
The website of Egypt's main daily newspaper Al-Ahram said Asfour, a writer, was under pressure from literary colleagues to leave the post.
Asfour was sworn in on January 31 and at the time he had believed it would be a national unity government, al-Ahram said.
There has been a renewed international element to the demonstrations, with Egyptians from abroad returning to join the pro-democracy camp. An internet campaign is currently under way to mobilise expatriates to return and support the uprising.
Protesters are "more emboldened by the day and more determined by the day", Ahmad Salah, an Egyptian activist, told Al Jazeera from Cairo. "This is a growing movement, it's not shrinking."
Meanwhile, 34 political prisoners, including members of the banned Muslim Brotherhood opposition group, are reported to have been released over the past two days.
There are still an unknown number of people missing, including activists thought to be detained during the recent unrest. Rights groups have alleged that the Egyptian army is involved in illegally detaining and sometimes torturing pro-democracy protesters.
Human Rights Watch said the death toll has reached 302 since January 28.
Egypt's health ministry has denied the figures, saying official statistics would be released shortly.