The figures could put more pressure on the European Central Bank (ECB) to increase stimulus measures ahead of its next monetary policy announcement on Thursday. There is growing pressure on the bank to start buying government bonds, although Germany has opposed the move to date.
Read MoreEuro zone GDP beats,Greece emerges from recession
The euro zone data was preceded by disappointing services PMI figures for Germany and France, the euro zone's largest and second-largest economies respectively.
The slowdown across the 18-country region reflected weakness in new order inflows, as new business fell for the first time since July last year. Job creation also remained near-stagnant, Markit said.
Chris Williamson, chief economist at Markit, said there were "worrying signs" of economic performance deteriorating in the euro zone's core countries, which, if sustained, "could drive the region back into recession."
Read MoreEuro zone moving from economic to political crisis
"France remains the biggest concern, suffering an ongoing decline in business activity, but growth has also slowed to the weakest for one-and-a-half years in Germany," he added.
Heightened geopolitical tensions, particularly related to Russia and Ukraine, have weighed on confidence and investment across the euro zone, according to Howard Archer, chief European and U.K. economist at IHS, reinforcing the challenging conditions in many countries.
Read MoreAs ruble tumbles, what will Putin do next?
"Credit conditions are currently still tight in many countries, unemployment remains elevated and seems likely to creep down at best over the coming months, private and public debt levels are high in a number of countries, while consumer purchasing power is constrained by generally limited wage growth," he said in a note Wednesday.
The weak November euro zone data are bad news for the ECB, Archer added, making it more likely that the ECB will eventually have to go down the quantitative easing (QE) route.