Smoke rises over the streets after a mortar bomb landed from Syria in the Turkish border town of Akcakale on Wednesday. Five people including a child were killed and at least 12 others were wounded.

The Turkish parliament approved a motion for cross-border military operations inside Syria on Thursday in an emergency session as tension escalated after a shell fired from inside Syria killed five Turkish civilians.

The motion, approved by 320 deputies in the 550-seat Turkish parliament, came as Turkish artillery hit targets near the Syrian border town of Tel Abyad for a second day on Thursday, killing several Syrian soldiers.

In the motion, the Turkish government said "aggressive action" against its territory by Syria's military had become a serious threat to its national security.

Calling it "a motion of war", it was opposed by the main opposition Republican People's Party.

A senior adviser to Turkish Prime Minister Recep Tayyip Erdogan, Yalcin Akdogan, a deputy from the ruling Justice and Development Party, argued that the motion does not necessarily pave the way for war, saying the opposition's criticism was based on "political" concerns.

"It's not a motion for war. It is a motion designated for future needs," Deputy Prime Minister Besir Atalay told reporters.

Turkey's priority was to act in coordination with international institutions on Syria, Atalay added.

The motion was drafted at an emergency cabinet meeting late on Wednesday, hours after five Turkish citizens were killed and a dozen others wounded in Syrian shelling of the southeastern border town of Akcakale.

Atalay added that Syria has admitted it was responsible for the shelling and has formally apologized for the deaths.

Atalay said on Thursday that Syria has reassured the UN that "such an incident will not occur again". Beijing-based military analyst Liu Linchuan said there is no doubt that Turkey intends to send troops to intervene in the domestic conflict in Syria, which had been part of the Ottoman Empire until the end of World War I.

"Turkey strongly wishes to build a pro-Turkey regime in Syria, and even to have a military presence in the country," Liu said.

But considering the strong feeling in the Arab world and among the Syrian people, Turkey is still waiting for a proper opportunity for possible military intervention in Syria, Liu said.

Foreign Ministry spokesman Hong Lei said on Thursday that China urges all sides to exercise restraint and refrain from taking any action that will escalate tensions in order to maintain peace and stability in the region.

Turkey's military response contrasted with its relative restraint when Syria shot down a Turkish reconnaissance jet in June. Ankara then increased its military presence along its 900-km border with Syria and called a meeting of NATO's North Atlantic Council.

That meeting was only the second time in NATO's 63-year history that members had convened under Article 4 of its charter, which provides for consultations when a member state feels its territorial integrity, political independence or security is under threat.

The same article was invoked for the NATO ambassadors' meeting in Brussels on Wednesday, after which they said the shelling was "a cause of greatest concern for, and is strongly condemned by, all allies".

NATO said it stood by member-nation Turkey and urged Syria to put an end to "flagrant violations of international law", and Turkey asked the United Nations Security Council to take "necessary action".

"I believe that military intervention by the West, in anything close to the scale of that which occurred in Libya, would possibly cause more damage, chaos, and instability than not," said David W. Lesch, a professor of Middle East history at Trinity University in Texas.

"Everyone is trying to insulate this so it doesn't spill over across into Lebanon or Iraq or elsewhere, or draw in the Israelis or the Turks, which may be impossible in the end, but I think everyone wants to prevent this from turning into a regional, or even an international, conflict," Lesch said.

In a letter to the president of the Security Council, Turkish UN Ambassador Ertugrul Apakan called the firing of the mortar bomb "a breach of international peace and security".

The White House said on Wednesday it stood by its "Turkish ally". But Ankara has found itself increasingly isolated and frustrated by a lack of international consensus on how to end the conflict.

UN diplomats said Security Council members hoped it would issue a non-binding statement on Thursday that would condemn the mortar attack "in the strongest terms" and demand an end to violations of Turkish sovereignty.

Members had hoped to issue the statement on Wednesday, but Russia asked for a delay, diplomats said.