Confronted with what it describes as a "major humanitarian catastrophe" in Syria, the Red Cross on Monday urged donors to more than double its budget this year to address the conflict in and around the war-torn country.

The International Committee of the Red Cross appealed to donors for an additional 62.3 million Swiss francs ($65.2 million, 50.5 million euros) to help it step up its response this year to the conflict inside Syria and in neighboring countries.

The deadly blasts that shook Turkey at the weekend will only spur Ankara to press harder for global action against the Syrian regime, analysts say, as fears grow that the country is being dragged into the spiraling conflict.

At least 48 people were killed Saturday in twin blasts in the town of Reyhanli, near the Syrian border, in an attack Turkey claims was masterminded by a group linked to embattled Syrian President Bashar Assad, though Damascus rejects the allegation.

The United States and Britain on Monday pledged to forge ahead with diplomatic efforts to end the civil war in Syria, saying they had found common ground with Russia on how to proceed.

U.S. President Barack Obama and British Prime Minister David Cameron vowed to increase pressure on the regime of Syria's President Bashar Assad, and insisted that he could not be part of a democratic transition.

The Swedish government said Monday U.S. Secretary of State John Kerry will arrive in Stockholm on Tuesday to discuss issues including the situation in Syria and the stalled Middle East peace process.

Kerry will meet his Swedish counterpart Carl Bildt and Prime Minister Fredrik Reinfeldt, the government said on its website.

Armed tribesmen kidnapped two expatriate employees of the International Committee of the Red Cross and their interpreter in southern Yemen on Monday, witnesses and militia sources said.

The Swiss and Kenyan ICRC staffers were abducted in the southern city of Jaar, which was held by loyalists of al-Qaida for 12 months until it was recaptured by the army in June last year, militia commander Hussein al-Wahayshi said.

Israeli Prime Minister Benjamin Netanyahu is to hold talks on Tuesday with Russian President Vladimir Putin on the conflict in Syria, the Kremlin said, amid concerns Moscow plans to deliver advanced missiles to the Damascus regime.

"During the meeting an exchange of opinion is planned on key aspects of bilateral ties," the Kremlin said in a statement.

Tribal gunmen kidnapped on Monday a Swiss man working for the International Committee of the Red Cross in southern Yemen, a local pro-government militia leader said.

The gunmen who belong to Al-Marakisha tribe kidnapped the man in the city of Jaar, in Abyan province, said Hussein al-Wahayshi, a local commander of the Popular Resistance Committees.

Syria's key National Coalition opposition group will meet May 23 to discuss a U.S.-Russian proposal for an international conference on a political solution to the Syrian conflict.

"The meeting will take place in Istanbul and last three days... to take a decision on the Kerry-Lavrov proposal and our participation," Coalition spokesman Sonir Ahmed told Agence France Presse, referring to U.S. Secretary of State John Kerry and his Russian counterpart Sergei Lavrov.

Vice Admiral John Miller, commander of the U.S. Fifth Fleet, said on Sunday that a massive naval minesweeping exercise involving 41 countries was not directed at Iran.

"It is not about Iran," Miller said at a news conference in the Bahraini capital Manama, the fleet's headquarters, saying the maneuvers were "purely defensive".

King Mohammed VI of Morocco has urged the conservative Istiqlal party to go back on a decision to pull out from the Islamist-led government, a spokesman for the party said on Sunday.

Istiqlal's national council, the main ally of the ruling Islamists, announced on Saturday it was pulling out of the government over its failure to shore up the economy and solve dire social issues.