Libya's embattled leader Moammar Gadhafi appears to have written to the U.S. Congress to praise its criticism of President Barack Obama over NATO raids on Libya, officials said Friday.

In the letter seen by Agence France Presse, Gadhafi comments on growing debate in Congress over whether Obama has usurped his constitutional authority by committing U.S. forces to the conflict without authorization by lawmakers.

Sudan's army has launched repeated air strikes on the southern army in Unity state in a bid to seize oilfields there weeks before the south's independence, a southern army spokesman said Friday.

Philip Aguer, spokesman for the Sudan People's Liberation Army (SPLA) of the south, said the SPLA was on "maximum alert" and strengthening its defensive positions, fearing the start of an invasion to seize the oilfields.

Syrian troops launched Friday a long-feared crackdown in the northwestern town of Jisr al-Shughour, as at least 22 civilians were shot dead by security forces when thousands of pro-democracy protesters took to the streets across Syria under the slogan "Friday of the Tribes."

Protesters poured on to the streets of main towns and cities after the weekly Muslim main prayers, many chanting slogans against President Bashar al-Assad and in support of residents of Jisr al-Shughour.

Pro- and anti-regime activists held rallies on Friday as loyalists celebrated news that Yemen's president was out of intensive care in Riyadh after treatment for bomb blast wounds.

Opponents of President Ali Abdullah Saleh intensified their pressure to form an interim ruling council, agreeing on seven names from across Yemen to be presented to Vice President Abdrabuh Mansur Hadi as candidates.

U.S. Defense Secretary Robert Gates piled pressure on Syrian President Bashar Assad on Friday, saying his very legitimacy was on the line after the "slaughter of innocent lives".

"The slaughter of innocent lives in Syria should be a problem and concern for everybody," Gates said after a speech in Brussels.

Turkish Prime Minister Recep Tayyip Erdogan accused the Syrian regime of perpetrating an "atrocity" against anti-government demonstrators, the Anatolia news agency reported Friday.

"I talked to Mr. Assad (Syrian President Bashar al-Assad) four or five days ago. ... But they underestimate the situation," Erdogan told Anatolia.

Israeli forces on Friday arrested a senior Hamas official in the northern West Bank, Palestinian security officials said.

Wasfi Qabha, 50, who had served as a minister for prisoner affairs in the Hamas government in 2006, was taken from his home in Jenin early on Friday morning the officials said.

The international Red Cross called Friday for immediate access to Syria, with its president Jakob Kellenberger saying he is ready to head to the country to discuss the issue.

"Vital humanitarian assistance must reach vulnerable people without delay," said Kellenberger, president of the International Committee of the Red Cross, adding that the relief agency was ready to deploy its staff.

The attack that injured Yemeni President Ali Abdullah Saleh was an assassination bid, likely an "inside job," using an explosive device, not a mortar or tank round, U.S. experts said Thursday.

STRATFOR, a U.S.-based authority on strategic and tactical intelligence issues, said its assessment was based on an evaluation of photographs taken of the blast site, a mosque inside Saleh's presidential compound in Sanaa.

Britain said Thursday it stood by allegations that Iran is helping Syria violently crush protests, after the British envoy in Tehran was summoned to the foreign ministry over the claims.

Iranian state television earlier reported that officials had told British Charge d'Affaires Jane Marriott that the comments by Foreign Minister William Hague on Tuesday were "based on a series of lies."