Egyptian riot police move forward to push back protesters during clashes in downtown Cairo, Egypt, in the early hours of Wednesday, Jan. 26, 2011. (AP Photo/Ben Curtis)

(CNSNews.com) – Protest organizers in Egypt called early Wednesday for a two-day national strike after a day of sometimes violent demonstrations described by observers as the most significant popular challenge to the 30-year rule of President Hosni Mubarak.

On the streets and online, many protestors and political groups are invoking the recent uprising in Tunisia, whose long-serving president, Zine El Abidine Ben Ali, fled to Saudi Arabia on January 14 after weeks of unrest.

Tunisia’s “Jasmine Revolution” has inspired demonstrations in Egypt, Algeria, Jordan and elsewhere, stoking speculation about a possible “domino effect” across a region where despotic and dynastic rule is the norm.

Tuesday’s protests in Cairo and other Egyptian cities were the most serious so far. At least two demonstrators were killed in the port city of Suez while the foreign ministry reported that a security force member died after being injured during clashes in the capital.

Some of the biggest skirmishes occurred in Cairo’s centrally-located Tahrir Square, where police used teargas to disperse more than 5,000 people, many of whom had earlier vowed to maintain a sit-in until demands for political and economic reforms were met.

Those demands include the scrapping of a three decade-old emergency law which among other things outlaws unauthorized demonstrations, an increase in Egypt’s minimum wage and, crucially, presidential term limits that would end the 82 year-old Mubarak’s long grip on power. Presidential elections are due later this year.

“First in Tunisia now in Egypt” reads the slogan on a poster held by anti-government protesters in downtown Cairo on Tuesday, Jan. 25, 2011. (AP Photo/Nasser Nasser)

Protestors also railed against the president’s son and presumed heir, Gamal. Unconfirmed Arab media reports late Tuesday said Gamal Mubarak and his wife, accompanied by large quantities of luggage, had flown out of Cairo for Britain.

Tuesday’s “day of anger” was organized by reform groups Kifaya (“Enough”) and the April 6 youth movement, and was largely promoted via Facebook, Twitter and other Web sites. Twitter reported that its service was blocked in Egypt on Tuesday evening.

Egypt’s biggest opposition group, the formally banned Muslim Brotherhood, also participated in the protests despite earlier claims by the Islamist group’s chairman, Mohamed Badie, that security personnel had summoned Muslim Brotherhood officials across the country and threatened them with arrests and violence should they take part.

The Muslim Brotherhood Web site early Wednesday reported the calls for an additional two days of protests, on Wednesday and Thursday.

Mubarak vs. Ben Ali

Egypt is the Arab world’s largest country (with a population more than seven times the size of Tunisia’s), a longstanding U.S. ally and the second-biggest recipient of U.S. military aid (after Israel).

The Obama administration’s response to Tuesday’s events was cautious.

Secretary of State Hillary Clinton urged restraint from “all parties,” but stopped short of criticizing the Mubarak government.

“Our assessment is that the Egyptian government is stable and is looking for ways to respond to the legitimate needs and interests of the Egyptian people,” she said during a joint media appearance in Washington with her Spanish counterpart.

In contrast President Obama, in hailing Tunisia’s political transition during his State of the Union address Tuesday night, declared that “the will of the people proved more powerful than the writ of a dictator.”

Whether Ben Ali deserves that epithet more than Mubarak is open to debate.

The Tunisian strongman seized power in a 1987 after having doctors declare his elderly predecessor medically unfit to remain in office. He won “elections” marked by candidacy restrictions and media curbs in 1989, 1994, 1999, 2004 and 2009, with official results giving him between 90 percent (2009) and 100 percent (1999) of the vote.

Democracy watchdog Freedom House in 2010 gave Ben Ali’s regime a score of seven for political rights and five for civil liberties (in an annual assessment where one is the best score and seven the worst).

Freedom House rated Tunisia “partly free” every year between 1987 and 1993, since when it has dropped into the “not free” category.

In Egypt, Mubarak became president in 1981 after the assassination of Anwar Sadat. He immediately declared a state of emergency which remains in force today.

Mubarak won “referendums” on his candidacy – there were no other candidates – in 1981, 1987, 1993, 1999, winning more than 90 percent of votes cast each time.

In 2005 he won a fifth term in what was billed as the first multi-candidate election, taking 88 percent of the vote according to official results. (His most successful challenger, Ayman Nour, was jailed for alleged election fraud soon after the election and remained in prison until released on health grounds in 2009.)

Freedom House in 2010 gave Egypt a six for political rights and a five for civil liberties. Egypt has earned the Washington-based watchdog’s “not free” designation every year since 1992. Before then it was rated “partly free.”

In an article posted on its Web site Tuesday, the Muslim Brotherhood said there were “many similarities between Egypt and Tunisia …  including rising food prices, high unemployment and anger at official corruption.”

“One of the main differences between the Tunisia uprising and that of Egypt, is that Egypt boasts a large force of well equipped, highly trained and very experienced riot police,” it continued. On the other hand, the article noted that Egypt has “a relatively free press.”