A sentence beginning with 'which' which isn't an interrogative sentence.

[police]

To the best of my knowledge, a sentence doesn't begin with 'which' unless it's an interrogative sentence, right?

Please take a look at this. This is an except of a long editorial.

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Indonesia, therefore, has some time been seen as a failing state; though the recent direct election of Susilo as the new president has raised hopes. Internationally (in the United States and Australia, particularly), Susilo is seen in a positive light as someone committed to fight terrorism.

Which brings us to a new facet of Indonesia's international image as the ideological center of Southeast Asian terrorism, inspired and directed by Jamaah Islamiyah. The organization is believed to be headed by the cleric Abu Bakar Ba'asyir, who is on trial for Bali and Marriott hotel bombings. It seems that Susilo's credibility with the United States and Australia would depend on having Ba'asyir convicted of terrorism and put behind the bars forever.

Undoubtedly, Ba'asyir deserves to be convicted if found guilty by proper judicial procedures and processes. Otherwise, it only creates a halo around him as someone fighting valiantly against not only his own government but also the mighty United States and its regional ally, Australia. And he is making good use of playing to the popular gallery.

http://www.koreaherald.co.kr/SITE/data/html_dir/2004/11/18/200411180012.asp

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As we can see, the first sentence of the second paragraph is stated with 'which' at the head. Is this a common way to say or considered a non-formal expression‎?

The corpus and google came across my mind but they didn't seem to be helpful this time. I'd love to hear anything from you.

[로빈]

먼저, [http://engdic.empas.com/show.tsp/?q=which&s=e]에서 B의 2의 b [선행하는 구/절/문 또는 그 내용을 받아]를 참조하세요. B의 2의 a[주격목적격의 경우]도 참조하시고요.

[police]

I've just read it through and and could see that such sentences are also used be informal sentences or formal ones. I thought I know almost everything about 'which' ,maybe I don't. Thank you, 로빈.^^