Hundreds of protesters were still camped out in Cairo's Tahrir Square Sunday following a night of bloody clashes with rival demonstrators loyal to the ruling military council.

Fierce battles erupted in the Abassaya neighborhood after anti-regime protesters were blocked from reaching the headquarters of the ruling Supreme Council of the Armed Forces (SCAF).

Iran on Sunday accused arch-foes the United States and Israel of masterminding the assassination of a scientist in Tehran, Dariush Rezaei-Nejad, who was reportedly associated with the defense ministry.

"The American-Zionist terrorist act yesterday against one of the country's scientists is yet another sign of the Americans' degree of animosity," speaker Ali Larijani told parliament on Sunday.

A suicide bomber driving a pickup truck killed seven people and wounded 18 others on Sunday when his payload detonated at a military camp in Yemen's main southern city of Aden, officials said.

Medics gave the toll, while soldiers told AFP the blast went off as troops prepared to leave the facility for Abyan province, where security forces are engaged in fierce fighting with militants suspected of ties to Al-Qaida.

Libyan leader Moammar Gadhafi heaped praise on toppled Egyptian leader Hosni Mubarak, describing him as "poor and modest" and saying he deserved honor rather than humiliation.

"I know Hosni Mubarak, a poor and modest man" who loves his people, Gadhafi said in an audio message broadcast on state television late Saturday to mark the anniversary of the 1952 coup in Egypt led by Gamal Abdel Nasser against the monarchy.

Fierce clashes broke out on Saturday in Cairo between protesters angry at the ruling military's handling of the transition from Hosni Mubarak's regime and army loyalists, an Agence France Presse correspondent said.

Around 1,000 protesters had tried to reach the defense ministry, the headquarters of the Supreme Council of the Armed Forces-- which took power when Mubarak was ousted-- but were blocked by barbed wire and armored personnel carriers.

Iranian nuclear scientist Dariush Rezaei was shot dead on Saturday when unknown assailants riding a motorcycle targeted him in the capital Tehran, local media reported.

"A physics professor and nuclear scientist was assassinated a few hours ago in front of his house in Tehran," Mehr news agency reported at 14:30 GMT.

Four Yemeni suspects have been arrested in connection with a car-bomb attack in the southern port of Aden that killed a British businessman on Wednesday, security officials said on Saturday.

The four suspects lived in the Moalla neighborhood where the attack took place, the security officials said, without ruling out further arrests.

Egypt's military ruler on Saturday stressed the army's commitment to democracy, as protesters kept up pressure on the general over the slow pace of reforms since a revolt ousted Hosni Mubarak.

Field Marshall Hussein Tantawi, the head of the Supreme Council of the Armed Forces and Mubarak's longtime defense minister, pledged to work for a free system through fair elections and a constitution.

Syrian security forces on Saturday arrested several civilians, including women, in the flashpoint central city of Homs where gunfire was also heard, activists told Agence France Presse.

"Gunshots were heard in al-Khalidiyeh neighborhood and security forces have been making arrests," Abdel Karim Rihawi, the head of the Syrian League for the Defense of Human Rights, said by telephone.

South Sudan rebel leader Gatluak Gai was shot dead in Unity state on Saturday, the army and a rebel source said, just a week after agreeing to a ceasefire and as the newly independent country renewed its amnesty offer.

It was unclear how Gai was killed, with the SPLA, the army of the south, insisting he was shot by his own men after reneging on the agreement, and a rebel source saying he was "murdered" by the SPLA.