Black-clad riot police fired rubber bullets from armored vehicles on Sunday to push protesters away from the ministry, while building walls of concrete on street entrances. Since Thursday, 12 people have been killed in Cairo and Suez, a hotbed of anti-government protests to the east of the capital.

Protesters demanding a swift presidential election and an early handover of power by the army hurled rocks at police guarding the Egyptian Interior Ministry on Sunday and were forced back with volleys of tear gas. It was the fourth day of clashes outside the ministry, in which seven people have died. Protesters accuse the ministry of failing to prevent the deaths last week of 74 people after a soccer match in the Mediterranean city of Port Said. Five more have died in Suez.

Some protesters believe that remnants of the government of ousted President Hosni Mubarak were behind violence that caused a stampede at the soccer match last Wednesday, and see it as part of a plot to create chaos to reassert their influence.

Political figures and a civilian advisory body to the military have suggested bringing forward a presidential vote to April or May, from the June date foreseen in the transition timetable of the army, which took power after Mubarak quit. Police and protesters, some waving flags of Al Ahli soccer team which played in Wednesday's match, hurled rocks at each other and police fired volleys of teargas to push the lines of mostly young protesters back from the ministry building.

The authorities erected fresh barriers of big concrete blocks barring access through streets leading to the ministry. Some earlier barriers had been hauled down.

"The demand is that the army step down politically and announce the start of nominations for the presidential election immediately," said Waleed Saleh, 30, an activist with a facemask at the ready, speaking near the ministry.

The military council, which took charge when Mubarak was toppled by a popular uprising on Feb. 11, has promised to hand power to civilians by the end of June after an election.

But calls for a swifter handover have mounted, and the Muslim Brotherhood which has the biggest bloc in Parliament, added its voice on Saturday to calls for a faster transition.

An army-appointed civilian council set up to advise the military is proposing accepting nominations for the presidency from Feb. 23, nearly two months sooner than the April 15 date previously announced. This could lead to a vote in April or May.

"If the army adopts that proposal, it will reduce the level of tension," said Saleh, who is also a member of the Lawyer's Syndicate, though he voiced a view popular among activists that the army might still try to influence policy from behind the scenes even with a president in place.

Saleh is among hardened activists who have kept a permanent presence in Tahrir Square since Jan. 25, the anniversary of the eruption of protests against Mubarak.

Other protesters also called for the army to quit now and demanded retribution after the soccer deaths and for those killed in protests. There has been intense speculation about the cause of the soccer stadium disaster, Egypt's worst.

"Those people over there are the reason for the deaths in Port Said," said 25-year-old Mahmoud Gaber, pointing to the police lines moments before a police riot car advanced and fired tear gas on youths in the street, briefly pushing them back.

Many are angry that there has not been a deep clear-out in the police force and that officers use the same heavy-handed tactics against protests as in Mubarak's era. The interior minister has blamed the incident on provocations by rival fans.

Many ordinary Egyptians are increasingly worried by the continued turmoil, and some see the army as the only institution able to guard the nation against a descent into complete chaos.

Newly elected independent parliamentarian Yasser Qadri, a member of the assembly's national security committee, said his committee was proposing drawing lines near state buildings.

"Those who cross the red line would be dealt with according to the law that gives security the right to protect state buildings from attacks," he said.

But that could prove a provocation to protesters who have ignored big concrete barriers.

Among the hundreds injured in the four days of clashes was Ahmed Maher, a leader of the April 6 movement which helped galvanise the protests against Mubarak. He was in hospital on Sunday with a head injury but was stable, the group said.

Meanwhile, an explosion hit a gas pipeline running from Egypt to Israel on Sunday, the latest in a series of attacks on the installation that crosses the increasingly volatile Sinai region, witnesses and state media reported.

The pipeline, which also supplies gas to Jordan, has come under attack at least 12 times since Mubarak’s ouster.

The latest blast took place in the Massaeed area west of the Mediterranean coastal town of al-Arish, in north Sinai. Gas pumping was stopped after the explosion.

In another development, the cases of 40 US citizens, other foreigners and Egyptians embroiled in a dispute over the activities and funding of pro-democracy groups have been referred to court, judicial sources said, deepening a row with the United States.

Washington has strongly criticized the crackdown on the nongovernmental organizations (NGOs) and an unspecified number of US citizens involved have sought shelter in the US Embassy.

Egypt, among the largest recipients of US aid since its 1979 peace treaty with Israel, has been told by US lawmakers assistance may be cut because of its treatment of the groups.

Several US and others involved have been barred from leaving Egypt. They include Sam LaHood, the country director of the International Republican Institute who is the son of the US transportation secretary.

“The cases of 40 foreign and Egyptian suspects have been transferred to the Cairo criminal court related to foreign funding,” a judicial source told Reuters. State news agency MENA also carried the report.

Egyptian officials say the crackdown is part of a probe into foreign funding of NGOs. But civil society groups say the ruling military council ordered the raids to harass activists who were at the forefront of the anti-Mubarak revolt and have been pressing for the army to swiftly hand power to civilians.

US Secretary of State Hillary Clinton said on Saturday a crackdown by Egypt’s military rulers on US and local pro-democracy groups could jeopardize aid for the Arab nation.

The NGO activists include 19 Americans alongside others who are Serbian, Norwegian, Lebanese as well as Egyptian, according to a statement issued by judges overseeing the probe and seen by Reuters. One judge involved said the list included LaHood.

The charge listed in the statement was “running organizations without getting the required licenses.” One of the judges running the investigation said that investigations were continuing with Egyptians in other similar cases.

Egyptian Foreign Minister Mohamed Kamel Amr told Clinton during his meeting with her that all groups, regardless of country of origin, had to abide by Egypt’s laws on registration, the ministry’s spokesman Amr Rushdy said.

The National Democratic Institute, one of the US-funded groups whose staff are facing travel bans, said it began work in 2005 and sought to register the same year but after responding to some official queries after that no progress was made.

However, the group says it has operated openly since then, engaging with officials regularly.