Four people including a child were killed in clashes Tuesday in south Yemen between security forces and separatists, who have called for "civil disobedience" in protest at the country's presidential polls, officials and medics said.

A 10-year-old child was killed when militants from the separatist Southern Movement traded gunfire with police near the election commission headquarters in Aden's Dar Saad neighborhood, residents and medics said.

Syrian forces killed 57 civilians Tuesday as they blitzed the city of Homs and a village in Idlib province, monitors said, as the Red Cross sought a truce to deliver aid and the United Nations demanded unimpeded access for aid groups.

The escalation comes as Russia, a key ally of President Bashar al-Assad's regime, said it will boycott an international conference in Tunis this week aimed at seeking political change in Syria and China refused to commit.

Russia on Tuesday said it will not attend an international conference in Tunis this week aimed at seeking political change in Syria because the meeting only supported the opposition's cause.

The meeting was called "for the purpose of supporting one side against another in an internal conflict," the foreign ministry said in a statement. "We cannot accept the offer to attend this meeting."

Yemen's future president Abdrabuh Mansour Hadi hailed Tuesday's election, in which he is the sole candidate, as a "historic day" that would open a new page for the country, as he cast his ballot amid tight security.

"This is a historic day in Yemen. We will turn the page of the past and open a bright new page on which we will write the future of a new Yemen," Hadi told reporters, as he posted his ballot into a box at a polling station in Sanaa amid applause.

Iraq's interior ministry said on Monday its forces had fended off "smugglers and infiltrators" trying to cross the border from Syria.

"Border guards were able to fend off groups of smugglers and infiltrators who were trying to cross the border from Syria into Iraq," a statement on the ministry's website said, without specifying when this occurred.

Top Republican U.S. Senator John McCain called on Monday for Syria's opposition to be given weapons to help "defend themselves" against President Bashar al-Assad's forces, while excluding direct U.S. aid.

"I'm not calling for the direct supply of weapons by the United States of America," he told a news conference in Cairo.

Outgoing President Ali Abdullah Saleh urged Yemenis to vote for his successor Abdrabuh Mansour Hadi in Tuesday's referendum-like elections to ensure a "peaceful" transition of power, state media reported.

"I invite you to actively participate in this democratic event and to head to ballot boxes to vote for Abdrabuh Mansour Hadi" as future president, Saleh said in a speech addressed to Yemenis, published by the Saba news agency.

Egypt says it is working "diligently" to resolve a bitter row with Washington over alleged illicit funding of NGOs for which American and other activists are due to stand trial, U.S. Senator John McCain said on Monday.

Egypt's military ruler Field Marshal Hussein "Tantawi has assured us they are working very diligently to resolve the NGO issue," he told a news conference in Cairo during a visit aimed at defusing the row between the traditional allies.

The Red Cross said on Monday it was negotiating with the Syrian authorities and opposition fighters to try to bring a halt to violence in the country so it can deliver vital aid.

"The International Committee of the Red Cross is exploring several possibilities for delivering urgently needed humanitarian aid," said spokesman Bijan Farnoudi.

Saudi King Abdullah on Monday met Tunisian Prime Minister Hamadi Jebali in the kingdom, where ousted president Zine el Abidine Ben Ali is living in exile, state news agency SPA reported.

The leaders discussed means of "developing relations between both countries" and "the situation in Arab countries," said SPA of the first high-level meeting between Saudi and Tunisian officials since Ben Ali was ousted in January 2011.