ISLAMABAD, Oct. 1 (Xinhua) -- Pakistani Prime Minister Syed Yusuf Raza Gilani told the parliament on Friday that Pakistan will consider other options if NATO continued intrusion into its sovereignty in future.

Pakistan says that NATO helicopters carried out three air strikes in its northwest tribal area of Kurrum Agency in a week, killing soldiers and civilians.

A NATO spokesman had defended the strikes and said that the action was taken after militants attacked an Afghan border post from the Pakistani side.

Pakistan lodged a formal protest with NATO in Brussels, calling for an end to such attacks in future, officials said.

"I want to assure you and the whole nation through this House that if intrusion into Pakistan's security is made, we will think of other options," said Prime Minister Gilani in the National Assembly after an opposition lawmaker raised the issue.

"Pakistan can in no way tolerate collateral damages by strikes inside Pakistan and will not allow anyone to interfere into our sovereignty and security," said the prime minister, warning that " If you (referring to NATO) do not explain it, compensate it or apologize it, we may consider other options too."