The United States on Monday condemned the Syrian army's incursions into Lebanon and suggested that dissidents of the Damascus regime had either been killed or taken prisoner at the border.

"Over the course of the last few weeks, it appears Syrian forces have entered Lebanese territory," a State Department spokesman told reporters, denouncing the move and calling on Syria to respect Lebanon's sovereignty.

Hizbullah and al-Mustaqbal MPs wrangled on Monday at the human rights parliamentary committee meeting which witnessed curses, threats and counter accusations.

The committee was scheduled to discuss a report by Internal Security Forces chief Maj. Gen. Ashraf Rifi on the alleged involvement of the Syrian embassy in the disappearance of Syrian opposition activists in Lebanon.

U.S. Ambassador to Lebanon Maura Connelly warned on Monday of the serious consequences Lebanon may face if it does not respect international obligations.

She reiterated, after holding talks with Free Patriotic Movement head MP Michel Aoun in Rabieh, the United States’ view that it is important to ensure that events in Syria do no create instability or tension in Lebanon.

Zahle bloc MPs slammed on Monday Hizbullah’s attempt to expand its military presence in the town of Tarshish, saying that it has completely disregarded the state and its constitutional institutions.

It also addressed Syrian army incursions into Lebanon, noting that its “shameful” position on the matter “demonstrates the extent of its affiliation with Syria that has not respected agreements between it and Lebanon.”

Syrian forces shot and killed four civilians Monday in the flashpoint central city of Homs, where troops were raking several neighborhoods with heavy artillery fire, a rights watchdog said.

The Syrian Observatory for Human Rights said one person was killed in the army's operations while the three others were shot dead by security forces and pro-regime militiamen.

The U.S. on Monday pulled its ambassador out of Syria what it said were security concerns, prompting a swift response from Damascus which recalled its ambassador to Washington a few hours later for "consultations."

State Department spokesman Mark Toner said that Ambassador Robert Ford returned to Washington this weekend after "credible threats against his personal safety."

The Parliamentary human rights committee session on Monday witnessed a heated debate over the discussion of a report written by Internal Security Forces chief Maj. Gen. Ashraf Rifi about the alleged involvement of the Syrian embassy in the disappearance of Syrian opposition members in Lebanon.

Voice of Lebanon radio reported that the voices were heard at the press room in the parliament.

U.S. Senator John McCain raised the prospect Sunday of possible armed intervention to protect civilians in Syria where a crackdown on pro-democracy protests has killed more than 3,000 people.

"Now that military operations in Libya are ending, there will be renewed focus on what practical military operations might be considered to protect civilian lives in Syria," McCain told a World Economic Forum meeting in Jordan.

European Union leaders are ready to slap more sanctions on Syria failing a halt in the regime's violence against dissenters, EU president Herman Van Rompuy said at the close of a summit Sunday.

EU leaders "expressed grave concern over continued brutality against the population in Syria," Van Rompuy said, adding that if the violence did not stop the bloc "will impose restrictive measures against the regime."

Syrian security forces reportedly killed three more civilians on Sunday as troops raided villages in the southern province of Daraa, cradle of the pro-democracy protests.

Activists had called for fresh protests on Sunday under the slogan: "It's your turn" -- a reference to Syrian President Bashar al-Assad -- hoping to force him out of power in the way Libyans ended the rule of Moammar Gadhafi.