Armed men opened fire on a security checkpoint early Wednesday in al-Arish, Egypt, on the Sinai Peninsula, state media said, three days after 16 border guards were shot dead in an attack on Sunday blamed partly on Palestinian militants.

Exchanges of gunfire continued late into the night, but there were no immediate reports of injuries, Egypt's official Middle East News Agency said.

"Unknown armed men opened fire on a checkpoint on the main road between al-Arish and Rafah," on the border between Egypt and Gaza, MENA said in a report also carried on Egyptian state television.

Meanwhile, the head of Egyptian intelligence, Morad Mowafi, admitted that the government had received intelligence warnings prior to Sunday's attack, Israel's Ynet News reported.

Speaking to Turkish news agency Anadulo following a meeting with Egyptian President Mohamed Morsi in Cairo on Tuesday, Mowafi said, "This incident should never raise any questions regarding the efficiency of the security forces in Sinai and their alertness." 

He said Egypt also had information regarding the "terrorist group" that committed the attack.

"Yes, we had detailed information about the attack, but we never imagined that a Muslim would kill a Muslim on the hour of breaking the fast in Ramadan," Egypt's intelligence chief told the news agency. 

Lawlessness in the rugged desert Sinai has spread since the fall of Hosni Mubarak 18 months ago and the election of an Islamist successor whose commitment to security cooperation with Israel has yet to be tested.

Wednesday's attack on the checkpoint was the 29th since the uprising, according to MENA, which also reported that security forces had closed the road where the assault took place.

Egypt's Al-Ahram Online news website reported that clashes erupted at three checkpoints in al-Arish on Wednesday between armed men and security forces and that one resident was injured while watching one of the clashes from the balcony of his home.

On Tuesday, Egypt began to seal off smuggling tunnels into the Gaza Strip, a security source told Reuters.

A Reuters reporter in the border town of Rafah said heavy equipment was brought to the Egyptian side of the tunnels, which are used to smuggle people to and from Gaza, as well as food and fuel that are a lifeline for the small territory's population.

"The campaign aims at closing all the openings between Egypt and the Gaza Strip that are used in smuggling operations," said the security source.

Security forces on Tuesday stormed the homes of several Egyptians in al-Arish who were suspected to have ties with jihadi groups and detained them pending investigations, according to security sources in Sinai.

Several Palestinian residents in the town who did not have official permits to enter Egypt were also taken to police stations for questioning, the sources said.

The government in Cairo said the gunmen behind Sunday's attack had reached Egypt via the Gaza smuggling tunnels.

No one has claimed responsibility. The Egyptian army said 35 militants were involved and that mortar bombs fired from Gaza landed in the area during the operation.

"Extensive meetings are currently taking place between top officials in the army, interior ministry and border guard to come up with a plan to detect and find the criminals behind Sunday's attacks," a Cairo security source told Reuters.

In Cairo, angry mourners at the guards' funeral chanted slogans against the Muslim Brotherhood, Al-Ahram reported.

Security forces were heavily deployed around the Al-Rashdan Mosque in the Nasr City district, and several of the surrounding streets were blocked off.

Getting close to the mosque, Ahram Online found families of the killed soldiers, as well as some public figures, mourners and many angry protesters.

The group was split between those who had made it inside the mosque to pray for the killed soldiers and the rest who waited outside in anger, chanting almost without pause and at times fighting with each other.

Protesters mainly chanted against President Mohamed Morsi and the Muslim Brotherhood, describing them as "betrayers of the country" and claiming that the Brotherhood collaborated with Hamas, which they accuse of involvement in the killing of Egyptian soldiers.

"Down with the rule of the Supreme Guide of the Brotherhood" and "The Brotherhood are agents and betrayers" were among the slogans that were chanted.

The infuriated protesters also kicked out any citizen whom they suspected to be a member of the Islamist group. Most bearded men were labeled as members of the Brotherhood and were forced to leave.

Morsi, who had been expected to attend the funeral, did not show up for "security reasons," while his newly appointed prime minister, Hisham Qandil, was attacked by angry protesters after attending funeral prayers. 

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