"It's been always a mystery the way incursions take place and the way they get timed with various visits... It's nothing new, it remains a mystery for all of us,” he told reporters at an interaction ahead of Indian Air Force's 82nd anniversary celebrations on October 8.
"You all know that in diplomacy a lot of signalling is done, especially so with our northern neighbour. It could be part of some signalling to my mind. But I am not going to guess what it really means," he added.
However, making it clear that India was "not giving ground to anyone", Raha blamed the frequent face-offs between Indian and Chinese troops along the Line of Actual Control on differences of perception between the two countries over the actual position.
"There are differences in perception as to where is the LAC... This is leading to face-offs. However, our security forces are following policies... We are not giving ground to anyone," he said.
Meanwhile, referring to the measures being taken to build military infrastructure along the border with China, Raha said that a fighter aircraft base is coming up at Nyoma in Ladakh, but added that the project would take about five years to be completed.
Another base would come up in Kargil, he said, adding that the funds will be released soon for it.
"These bases are strategically important for us and will improve our capabilities," he said.
Upgrade of six airfields in the northeast is also being carried out and the work will be completed by the end of 2015.
That would allow air force to operate fixed wing aircraft from there for swifter force mobilisation, Raha said.

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