ISLAMABAD, April 28 (Xinhua) -- As many as 70 militants have been killed in the operation against them in northwestern Pakistan, the Interior Minister Rehman Malik said on Tuesday.

Speaking to reporters here, Malik said 70 militants had been killed till now in Dir district of North West Frontier Province (NWFP) and 450 militants were still present in Buner District.

He said the militants should leave Buner District. Serious action will be taken against those who challenge the writ of the government, he said.

Pakistan Army launched an operation against militants in Dir district on Sunday as tension prevailed in some parts of NWFP including Swat valley.

Sufi Muhammad, founding chief of an outlawed organization struck a deal with NWFP government in February, according to which the government promulgated Nizam-e-Adl to enforce Shariah, or Islamic law, in Malakand division and the Taliban in Swat ceased fire.

The Taliban in early April entered Buner district from Swat and set up check points and patrolled the area with armed men. The NWFP government, Sufi and Taliban held successful talks last week and Taliban withdrew from Buner.

The army has been engaged in operation in Dir district against militants for the last few days, killing scores of militants. Sufion Monday announced talks with the government had been suspended because the operation was against the peace agreement, he believed.