Violence in Iraq killed 18 people on Sunday, as ordinary Iraqis poured scorn on the authorities for failing to stem a weekend of unrest that cost dozens of lives.

More than 540 people have been killed so far this month and over 2,800 since January 1, according to Agence France Presse figures based on security and medical sources.

British Prime Minister David Cameron said on Sunday that the Syrian conflict was "on the wrong trajectory", admitting the Assad regime may be getting stronger, and urged more help for opposition forces.

"It's very depressing picture and it's a picture that is, I think, on the wrong trajectory," Cameron said in an interview with the BBC.

Gunmen killed two Egyptian soldiers and a policeman on Sunday in three separate attacks in the restive Sinai peninsula, which borders Israel, security and medical sources told Agence France Presse.

The unidentified assailants in the town of El-Arish shot dead one soldier in front of the television and broadcasting building and another who was on guard duty, and killed the policeman in an attack on a police station, a security source said.

Egypt's new cabinet held its first meeting on Sunday and urged parties to keep their demonstrations peaceful, as a panel named to amend the constitution called on all sides to contribute.

In the latest violence, militants in the restive Sinai killed two soldiers and a policeman. Supporters of ousted Islamist president Mohamed Morsi, meanwhile, called for fresh rallies at foreign embassies in Cairo.

Deadly violence raged across Syria on Sunday as regime shelling killed at least 18 civilians in the northwest while 28 rebels died in Damascus battling government forces, a monitoring group said.

The latest bloodshed came as Deputy Prime Minister Qadri Jamil was due to travel Monday to Moscow for talks with Russian Foreign Minister Sergei Lavrov on ways of ending the 28-month conflict.

Gunmen suspected of being members of al-Qaida kidnapped an Iranian diplomat in broad daylight on Sunday in the Yemeni capital Sanaa, police said.

"An Iranian diplomat was abducted on Sunday in Sanaa by armed men," a Yemeni security source told Agence France Presse, adding that the envoy was "taken to an unknown destination."

Iran on Sunday voiced opposition to a U.S.-mediated resumption of peace talks between Israel and the Palestinians, predicting the Jewish state would never agree to withdraw from occupied Arab lands.

Tehran "along with Palestinian groups expresses its opposition to the proposed plan and it's certain that the occupying Zionist regime will utterly not agree to withdraw from the occupied lands," foreign ministry spokesman Abbas Araqchi said, quoted by Iranian media.

The Arab League said on Sunday it supported the Palestinian stance on the announcement of resumed peace talks with Israel, but that it was skeptical of Israeli intentions.

The League "is forming a political support network for the Palestinian side in case it accepts to go to the negotiations with the Israeli side," Mohammed Sabih, deputy secretary general for Palestinian affairs and occupied Arab territories, told reporters.

A military court on Sunday rejected a bail application by Islamist cleric Abu Qatada, who faces terror charges in Jordan following his deportation from Britain, his lawyer said.

"The state security court today refused to release Abu Qatada on bail," Taysir Diab told Agence France Presse.

A road accident killed 15 soldiers and injured another 40 early on Sunday in Egypt's Nile Delta province of Beheira, a security source told Agence France Presse.

Their bus collided with a lorry on a highway in the province, leaving 15 of them dead and another 40 injured, the source said.