Depending on what parties end up in parliament, Merkel could also find herself leading a "grand coalition" government with the left-leaning Social Democrats or -- less likely -- with the environmentalist Greens.
"This is a super result," said Merkel, Germany's chancellor since 2005 and the de facto leader of the response to Europe's debt crisis over the past three years.
Merkel said it was "too early to say exactly how we will proceed" in forming a government.
If her current coalition lacks a majority and the conservatives can't govern alone, the likeliest outcome is a Merkel-led alliance with the Social Democrats. The two are traditional rivals, but governed Germany together in Merkel's first term after an inconclusive 2005 election.
"The ball is in Merkel's court," her center-left challenger, Peer Steinbrueck, said. "She has to get herself a majority."
Merkel's conservative Union bloc won about 42 percent of the vote, an improvement of more than eight points over Germany's last election in 2009, according to ARD and ZDF television projections based on exit polls and early counting. Her coalition partners of the past four years, the pro-business Free Democrats, were just below the 5 percent level needed to claim seats in the lower house, according to the projections.
Nevertheless, the Union's strong showing was a personal victory for Merkel, solidifying her position as Europe's strongest political leader.
"We will do everything together in the next four years to make them successful years for Germany," Merkel said. Merkel was interrupted by cheers and chants of "Angie! Angie! Angie!" as she made a brief appearance at her party's headquarters.
Steinbrueck's Social Democrats trailed well behind Merkel's party with up to 26.5 percent, projections showed. Their Green allies polled 8 percent, while the hard-line Left Party scored 8.5 percent. The Left Party includes heirs of East Germany's former communist rulers, and the center-left parties say they won't form an alliance with it.
"We did not achieve the result we wanted," Steinbrueck told supporters. He said that he wouldn't engage in "speculation" about the next government.
It wasn't clear whether a new party that calls for an "orderly breakup" of the eurozone, Alternative for Germany, would win seats in parliament's lower house. The exit polls showed them winning up to 4.9 percent -- just shy of enough for seats. Merkel and others have said they won't deal with the party.
Labor Minister Ursula von der Leyen, a conservative, said it was an "overwhelming" result for Merkel's party.
"The important thing is that Germany has stable conditions," she said.
The exit polls were greeted by shocked silence at the Free Democrats' election event. Four years ago, the party won nearly 15 percent of the vote, its best-ever result -- but the party has taken much of the blame for squabbling in Merkel's governing coalition since then.
"It's the bitterest, saddest hour of the Free Democratic Party," the party's leader, Vice Chancellor Philipp Roesler, said.
Merkel's party ran a feel-good campaign that centered squarely on Merkel's personal popularity and, opponents complained, largely avoided controversial issues. Recent polls gave her popularity ratings of up to 70 percent, but the sky-high ratings didn't extend to her coalition.
Merkel has called her current coalition "the most successful government since reunification" 23 years ago. She pointed to the robust economy and unemployment which, at 6.8 percent, is very low for Germany and far below that of many other European countries.
Germany's first post-war chancellor, conservative Konrad Adenauer, won the only single-party majority so far in 1957. He formed a coalition with a smaller party anyway, but the Union governed on its own from mid-1960 to late 1961 after most of that party's lawmakers defected to it.
The new Alternative for Germany's leader, Bernd Lucke, said it had "taught the other parties to be scared," whether or not it enters parliament. The party appealed to protest voters on the right; Lucke said it had "strengthened democracy in Germany."
Merkel has pursued a hard-nosed course in the euro crisis -- insisting on spending cuts and economic reforms in exchange for bailout struggling countries such as Greece. The bailouts haven't been popular, but Germany has largely escaped the economic fallout from the crisis, and Merkel has won credit for that.
Europe played only a very limited role in the election campaign. It was dominated by domestic issues such as center-left calls for tax increases on high earners and a national minimum wage, which Merkel rejected.
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