Turkish PM also warns that armed forces will respond to any Syrian encroachment on the border

Turkey's prime minister, Recep Tayyip Erdoğan, has threatened Syria with retaliation for the shooting down of a military jet, and warned that Turkish armed forces would respond to any Syrian encroachment on their joint border.

The warning from Ankara came as opposition activists reported 92 people killed across Syria and Russia signalled that it would take part in new diplomatic attempt to end the crisis. The UN's head of peacekeeping told the security council that monitors were still unable to operate because of the risks they faced.

Erdoğan described the downing of the reconnaissance plane on Friday as a deliberate and hostile act that would not go unanswered.

The rules of engagement for Turkish forces along the Syrian border had been changed so they would respond more forcefully to threats coming from Syria.

"Any military element that approaches the Turkish border from Syria by posing a security risk and danger will be regarded as a threat and treated as a military target," Erdoğan said.

Ankara has accused Syrian gunners of targeting a Turkish search-and-rescue plane looking for survivors from the downed jet on Saturday. Turkish officials said the rescue plane had agreed its route with the Syrian authorities but came under fire nevertheless, causing the rescue mission to be suspended. On Tuesday morning the prime minister claimed Syrian helicopters had violated Turkish airspace five times recently without a Turkish response.

Erdoğan suggested any further violation would be met with force, adding that any Syrian military element seen approaching the Turkish border would be regarded as a threat.

But the Nato secretary general, Anders Fogh Rasmussen, made it clear that the alliance was not considering a collective armed response. Following an emergency meeting in Brussels called by Turkey to discuss the downing of the Phantom F-4, Rasmussen said the allies "expressed strong condemnation of this completely unacceptable act" but said the possibility of invoking article five of the North Atlantic Treaty, under which all allies intervene to defend against any attack on any member state, had not been discussed.

"We stand together with Turkey in spirit of solidarity," Rasmussen said. But when asked how Nato would respond if there was another such incident, the Nato secretary-general said only that the allies would once again "consult", while remaining "seized of the situation". He said he did not think there would be a repeat of the incident.

Turkey said its jet had unintentionally strayed into Syrian airspace while on patrol but had been shot down over international waters.

Turkish political observers say that the rare formal consultation with Nato allies (under article four, which has only been invoked once before, by Turkey in 2003) and Erdoğan's heated rhetoric is designed for domestic public consumption, to compensate for the absence of any direct retaliation.

However, the warning that any Syrian military movements near the Turkish border would be perceived as a threat appears to be a signal that Ankara would respond with force against any Syrian army attacks on rebels on or near the frontier and could open the door to wider Turkish military involvement. Turkey is already reported to be participating in the arming of the rebel Free Syrian Army.

In a move that may herald greater Russian cooperation over Syria, the country's foreign minister Sergei Lavrov is to attend a meeting on the conflict that international mediator Kofi Annan trying to organize in Geneva this weekend. "We attach great importance to this meeting, said Vitaly Churkin, Russia's UN ambassador.

Annan's deputy Nasser al-Kidwa on Tuesday briefed the security council on Annan's attempts to prevent the collapse of his moribund six-point peace plan.

The head of UN peacekeeping operations, Herve Ladsous, said the 300-strong monitoring mission in Syria would remain suspended because of the violence.

The Local Coordination Committees, an activist network, reported 56 dead, 20 of them in the suburbs of Damascus, where loud explosions were heard from the early morning.