The alleged incursion happened near Tall al-Abyad

The foreign ministry in Pyongyang called the claims an "unskilful conspiracy" and "groundless".

There were allegations last week that Syria was holding technology or materials relating to North Korea's nuclear programme.

This follows reports that Israeli jets entered Syrian air space earlier this month and hit an unknown target.

"Recently some US media including the New York Times have been spreading allegations that we are secretly helping Syria with its nuclear programme. Such reports are groundless and misleading," a ministry spokesman said.

He also dismissed reports that North Korea could be helping Syria build a nuclear weapons facility.

"We, as a responsible nuclear power, already declared in October 2006 that we will never allow the transfer of nuclear materials, and we have been sticking to this declaration," the spokesman said in a statement published by the official Korean Central News Agency.

The suspicions were "nothing but an unskilful conspiracy" fabricated again by "impure forces" who do not want to see "progress in six-party talks and in relations between Washington and Pyongyang", the spokesman added.

No comment

Syria has formally complained to the United Nations about the alleged raid by Israeli aircraft over its territory.

Israel has repeatedly refused to comment on the alleged raid.

There has been speculation over what the likely targets of the Israeli raid may have been.

One, cited by the New York Times newspaper quoting a US source, suggests that the attack was in some way linked to North Korea.

The former US ambassador to the UN, John Bolton, in a recent article in the Wall Street Journal, raised the possibility that Syria was sheltering technology or materials relating to North Korea's nuclear programme.

Another suggestion is that maybe a missile store or factory with weaponry heading to Hezbollah in Lebanon was hit, says BBC diplomatic correspondent Jonathan Marcus.

Israel has long complained the Damascus government is at the very least turning a blind eye to such weapons supplies coming from Iran, our correspondent adds.

Syria and Israel remain technically in a state of war.